WMG / DARLING in the FRANXX

Hiro and Zero Two Theories

Zero Two is a hostage of some sort for the military.

Zero Two complains about wanting to swim in the ocean in the first episode and brings up running away to Hiro before brushing it off as a joke. It seems that if she wanted to leave, she could easily hop in Strelizia and do so (considering Zero Two already does whatever she wants most of the time). There seems to be something preventing her from leaving that may require Hiro's help. And Zero Two's reputation as a "partner killer" may stem from the fact that she's trapped and her killing streak is a form of lashing out at the plantation defense squad.

• With how it's shown Zero Two had been searching for the one that can become her darling before meeting Hiro, it's likely she stayed because the adults had been throwing prospective partners at her at any given opportunity. Thus, making her search easier though it may not be to her liking. It would seem unlikely she would be able to achieve anything if she really did decide to take a hike somewhere else and leave the Plantations behind.
• Episode 13 shows that she's been searching for her Darling, alright... the one being Hiro himself as they had actually met when they were kids but Hiro forgot everything after getting his memory wiped, thus triggering his own problem with Mitsuru to this day.

Ichigo and Hiro are actually brother and sister.

Their numbers are similar, similar hair and eye colors, and Zero Two likes both their tastes.

• Wouldn't they have mentioned a connection like this by now? Also, if that is the case, considering what piloting one of the FranXX has been compared to...ewwww.
• Jossed. Parasites are vat-grown and it's implied Squad 13 especially was given a lot of genetic variance.

Zero Two has to constantly kill Klaxosaurs to maintain her humanity

After Hiro survives his third flight with her, she muses that she'll have to keep killing them - the "so I can stay with him" goes unsaid but is clearly implied. Strelizia has a tube connecting its weapon to the body of the frame, and while this could be to do with powering/reloading it, none of the other Franxx with reloading weapons have a similar link meaning it might provide something from the destroyed cores back to the neural link system. Additionally, the Strelitzia is a genus of flowers with long, brightly-colored protrusions essential to reproduction. Finally, as of Episode 10, Zero Two is behind on her meds. Having missed the last two cores (one blown up by Delphinium, one kill stolen by Argentea), she's starting to lapse, and her fangs growing is but the first symptom - she knows this, and that's why she was moody in the hanger. She's not speaking up because the squad is used to handballing Strelizia the kills anyway, and she possibly fears this would lead to a rejection when they realize she still poses a risk to everyone around her.

• Almost all addressed in episode 12:
  • Jossed: The tube is just a fuel line, Strelizia doesn't actually adsorb anything.
  • Confirmed: Zero Two absolutely is mutating, and does want to kill Klaxosaurs to maintain her humanity...
  • Grey area: ...but she appears to be taking a metaphor literally in thinking it will work, which is pushing her off the deep end, and her feelings toward "Darling" are getting muddier by the minute as her past is dredged up.

The reason Hiro's memories returned...

Was due to the regenerative properties of the klaxosaur blood he ingested into his system before his mind-wipe once its genetic code grew strong enough from synchronizing enough with Zero Two which triggered his "saurification" from exposure from her. The klaxosaurs are already proven to heal from anything as long their cores are intact and Zero Two herself got an amazing healing factor the scientists explored in gruesome thoroughness in her childhood, so when Hiro ingested it he got a genetic back-up of his brain before whatever the doctors did to him damaged his memory lobes to forget. In short, he's developing a Healing Factor like Zero Two and it was strong enough to regenerate lost nerve patterns and ends that once contained his memories.

• It's more probably because Hiro got his memory jolted back when his own mind was linked to Zero Two's at the start of Episode 13. Zero Two remembers everything and that may have served as the cornerstone of him regaining that small part of lost memory.

Zero Two is not the only one who is a Klaxosaur-Human hybrid

During the scene where Zero Two was first experimented on in Garden, Franxx mentioned that there were other specimens but Zero Two was the only one to have developed a full human form. Based on how Zero Two was actually called Nine Iota, the previous eight of that particular group may all be hybrids despite her code number being 002. With how Zero Two is able to maintain a near human-like appearance up to this day, the others may be doing so too.

The reason for Zero Two's regression and saurification.

Is due to her exposure to Hiro while in the Franxx, just as he's progressing into a klaxosaur's genetic code from being in exposure to her.

• Ironically it may be that Zero Two was only led to believe that if she killed enough Klaxosaurs she would become human when in reality it is the life force that she consumes from the stamens that ride with her that maintain her human appearance. Her regression from episode 10 and on is from having not devoured Hiro (or anyone else) in such a long time. APE knows this as at the end of episode 14 she was introduced to a dozen new stamens with Nine Alpha telling her to use as many as she likes.

Zero Two will not abide by the "three rides only" rule anymore.

As her saurification increased after episode 14 (with the length of her horns as a hint), her toxicity will spike to the roof with them and make it impossible for any stamen to ride with her more than once before being drained dry and dead in the cockpit. She's going to plow clean through the volunteers like candy and to such extent that APE will have no other choice but pair her up with 016 (Hiro) again, just so they won't lose all of their stamens to Zero-Two's body.

• She did eat them all, but APE had nothing to do with Hiro's actions.

The reason Zero Two was so cold to Hiro right before the reveal

Is because she was afraid. She was the happiest since the escape, and she was liking him more and more. She got scared he will replace her 'first darling' in her heart and had to convince herself he is just another stepping stone towards her goal.

• It's also possible she felt betrayed, having thought she found her first darling again but, as attempt after attempt to jog his memory kept failing, she convinced herself it was a case of mistaken identity and she got hostile with him for taking advantage of her. That was in no way Hiro's fault, but she wasn't in the most rational state of mind by the time she reached that conclusion.

Naomi will come back and her return will throw a spanner in the works in regard to Hiro's "relationships"

She's clearly quite important to Hiro, since she's the first person she thought about when he was near death (even though she survived), and their interactions have a hint of being Amicable Exes. A return down the line could possibly be a major source of tension and drama for Hiro and the two girls in his life.

• After what happened in Episode 12 and 13, this seems unlikely to happen as the two episodes stapled who is the most important person for both Hiro and Zero Two.
• Partially confirmed in Episode 22. Naomi is revealed to be alive and returns to the show. Given Hiro's devotion to Zero Two (and the fact that they both die in the series finale), however, the second part is Jossed.

Hiro and Zero Two were having sex during the one-month Time Skip

While the show doesn't explicitly confirm it (unlike the plot-relevant example), consider the evidence:

• They're both sharing a private room with one bed - while they're never seen in it, they frequently share a blanket.
• Zero Two had already put the idea of "what happens after kissing" in Hiro's head, and it's likely he'd want to explore that now their relationship was more secure.
• The pair of them are more tactile than ever, frequently in each other's personal space. While Hiro does hesitate to hold hands at one point, it's due to the romantic atmosphere, not fear of touch.
• When Zorome accidentally outs Kokoro and Mitsuru for getting intimate, it's because he asked if "putting your bodies together" was a new trend. If he'd just meant kissing, he would have said kissing, suggesting he might have caught Hiro and Zero Two getting comfortable with each other.
• As for why it never gets the same reaction as the other couple, they simply kept such an intimate act to themselves, and they were doing it out of love for each other, not a desire to reproduce - considering both of them have been put through the genetic wringer it's doubtful they could conceive viable offspring anyway.

Plantation 13 Theories

The Parasites will go rogue and escape the Plantation.

• Episode 13 actually shows that Hiro tried this as a kid with Zero, with no success as he was simply a child with no resources to help and they were quickly found and brought back to Garden to have their memory wiped

Everyone is some sort of Artificial Human.

It's odd that the protagonist and his friends don't have any given names, isn't it? It's like they're mass-produced or some-such.

• Adding on to this, nobody knows where the failed Parasite candidates go. For all we know they could be killed and recycled to produce new candidates. And not to mention the fact that they're called Parasites. It's odd that the saviors of these plantations have such a negative name attached to them.

Kokoro and Futoshi are either faking their cutesy relationship or hiding something extremely dark.

• They've had very little screen-time, both of their defining characteristics is being "the nice, gentle one," they're supportive of one another, they don't seem to have any hangups, they're "lovey-dovey" with each other... in this cast? In this series? I don't trust it at all. There's something going on there.
  • Or it could just be that they're the Sickening Sweethearts of the show.
  • To add onto this: Futoshi and Kokoro have the lowest sync rates of the main team. And in an interview, Saori Hayami (Kokoro's VA) has described her impression of Kokoro being "a character whose personality has turned 180 degrees around when compared to the image [she] had of her during the audition".
• Episode 11 explains that despite Futoshi really does like Kokoro, it's her who does not really have much feeling towards him. In the end she ends up with Mitsuru as her partner, leaving Futoshi drowning in his tears.

The Plantation 13 kids are the adult's attempt to recreate Strelizia/002's power

• Considering all the Plantation 13 Franxx are modelled specifically after their pistil/female pilots, while Plantation 26 uses a standard model for all pairs raises some questions.
• A follow on to this: Those that failed out of the program (like Naomi)became pilots of regular FranXX, which is how the other plantations have heard of Hiro.
• Standard Franxx units seem to have a fuel gauge as one of the Squad 26 units actually ran out of fuel mid fight while Squad 13's Franxx units haven't shown to suffer from such consequences...for now. They even need to replace used magazines for the weapons to work while Squad 13's seem to have the power source built in and replenishes spent energy of their weapons naturally. Everything Squad 13's assigned Franxx can do, Strelizia seems to be able to do better. 13's Franxx would really seem to be something created to try and replicate Strelizia's overall capabilities, don't they?
• Episode 9 tells that all Franxx, even those of Squad 13 and Strelizia use fuel. The reason that one from Squad 26 ran out out fuel is probably because they have been the most active on the battlefield before Squad 13 went all out.

The children and Franxx pilots...

Are in fact petris-dish hybrids, infused at various stages in their lives with Klaxosaur blood, but too human to manifest any serious klaxosaur traits akin of what the 00-Series are (Zero-Two for example), hence why they are kept at a flagpole's length from the plantation and all of the adults. They are practically Tyke Bomb klaxosaurs in the making and whenever a child is sent away, it's in fact sent into the wasteland outside where it develops fully into a klaxosaur which instantly set a course back to the plantation where it originated from, driven by instinct, in order to find what it feels is missing inside.

The reason Nana had a mindwipe

• The mindwipe is made obvious in episode 17 (as she begins to recover the memory). She was mindwiped because she was the pistol piloting the FranXX that captured Zero Two.

Dr. Franxx and APE Theories

Dr. Franxx has an agenda that is not APE's.

• This goes with the idea that Squad 13 is an attempt to duplicate Strelizia, above. The Beach trip was entirely Dr. Franxx's idea, meaning he wanted Squad 13 to find that old, abandoned city by the seaside, and the various consesquences that might arise from seeing that other world.
• Episode 8 hints that the current Squad 13's personnel and equipment setting is all Franxx's idea,not the work of other adults though it may have something to do with having the pilots cope better with the term of growing up.
• Episode 13 shows that he's very much a member of APE, it's just that he's more open-minded to possibilities of change in approach.

Dr. Franxx built both the Klaxosaurs and the Franxx to force a better way of life.

Drilling for the magma ruined the Earth. The cities are emotionless, but he still gropes an ass. He never talks about APE in a respectful manner. Klaxosaurs look like robots. His best anti-Klaxosaur squad lives their lives in the old way. By weakening APE on one side and showing how their best defense comes from what they hate on the other, he will unmake the world that APE has created.

Dr. Franxx has a personal history with the Klaxosaur Princess

It's clear that Dr. Franxx approaches things differently than the rest of APE, and it's likely he has a different endgame in mind as well. The introduction of the Klaxosaur Princess (let's call her Zero One for now) in Episode 16 may clarify the doctor's true objectives. What is his goal, you may ask? Simple: to reunite with Zero One.

If this redditor's theory is anything to go by, I'm willing to bet that Dr. Franxx met Zero One a while back. Much like our Official Couple, the two fell in love but Zero One runs away when she realizes she's killing Dr. Franxx. In his grief, he develops the Franxx mechs and helps APE's parasite program all so he could eventually find a way to come back to Zero One. This would effectively make the two not only tragic villains, but also one hell of a Shadow Archetype to Hiro and Zero Two (the Blue Oni to Hiro and Zero Two's Red, if you will).

• Yes and no. Franxx did meet with her when he was younger, resulting in him becoming a cyborg and creating Zero Two from the DNA in her hair.

APE has hidden the actual franxx/klaxosaur history

.The current story of magma mining awakening them seems off. Dug Too Deep makes sense at first glance, but since we've found that magma attracts klaxosaurs, why did they keep mining, bringing more? The only way to use magma as a fuel source is much the same as we use nuclear power now: heat water into steam which turns turbines that provide work. The sky seems clear, why not attach solar panels and wind turbines to the outside of the plantation? Or just mine uranium. Perhaps the Franxx were initially designed as the latest in military design (supported in episode 5 when the plantation 26 squad comments that squad 13's mechs are all basically Ace Custom), but issues resulted in the two pilots gradually fusing with their mecha, becoming what we know as the klaxosaurs. This led to a major world conflict that resulted in the move to the plantations. Those loss of some technologies but not others led to the Franxx's being upgraded in order to compensate, but this only made the pilots degrade faster. This is why the klaxosaurs seem to have human bodies in the core. As a franxx pistil/stamen, you either die a hero or live long enough to see yourself become a klaxosaur.

The sexual nature to FranXX piloting isn't necessary to their function; Dr. Franxx deliberately engineered them that way.

This theory hinges on the idea that Dr. Franxx intends to restore humanity from the bleak, sexless, lifeless existence that APE has engineered. By engineering the principal weapons against APE's great enemy to only be able to function in the hands of pilots in a sexuality-based partnership, Franxx effectively forced APE to preserve a small fraction of humanity with intact sex drives and emotional spectra.

• Or it might just be that he'a Dirty Old Man? One of the first things in episode 1 we seem him do is grope Nana fairly publicly in the workplace after all.
  • It might be a bit of both.

Dr. Franxx is Hiro's biological father.

And he used the genetic materials of his wife, Dr. Karina Milse, as the biological mother, in order to honor her memory and wish of having a child of their own, resulting in Hiro.

Klaxosaur Theories

Klaxosaurs have a precise reason for attacking the city/By the time the series ends, the current society will fall

Shady adults, memory manipulation, use of expendable teenagers. There's some sort of secret (a la the hidden body of Lilith in NGE) that draws them in. what is another potential WMG of its own.

• This relates to the second one: due to things being eventually revealed and other things hitting critical mass, the emotionally suppressed society will fall as a new one rises. And relate to a few other WMGs, Dr. Franxx would approve of this if not aid said secret unveiling.

The Klaxosaurs will end up joining the Plantation 13, reluctantly or not

If the "Klaxosaurs are Humans" theory is confirmed.

At least some of the Klaxosaurs are actually the parasites who disappeared from the Garden

It is strongly implied that the missing children died and were just disposed of, but the "Yellow Blood Cells" could have done something to the bodies. Dump enough of them in a hole, and they might become Klaxosaur cores.

The Klaxosaurs are somehow related to Humanity's abandonment of reproducing in exchanged for Immortality

It seems a little suspicious that over 80% of humanity has undergone the immortality procedure when the Klaxosaurs first appeared. The fact that Dr. FranXX (back when he was just Werner Frank) found that the Klaxosaurs have near identical X-chrmosones to human female adds to this. Plus when he meet with the Klaxosaur Princess she noticed that he had the scent of her brethren. Weather this meant other Klaxosaurs or humanity pre-Imortality is WMG on it's own. Her calling APE "wannabe humans" also helps.

Setting Theories

The colonies are ghettoized hellholes

All that shiny futuristic stuff? That's exclusively for the military and the political elite.

Not counting security personnel and the APE council, there have been six on-screen adults as of episode 10

These are Nana, Hatchi, Zero Two's unnamed dead man of a partner, the Professor, the old lady, and her "partner". Everyone else has been a hologram. In the first episode, all the onlookers of the Parasite ceremony briefly stutter when the plantation was attacked. The adults at the plantation kissing ceremony never interacted with anything they weren't already holding when they first appeared. Even at the medal ceremony, the adults never physically present the medals or interact with the kids - and a superior officer showing respect by attaching the medal is very potent symbolism in any version of the ceremony that would have been dug up to copy (assuming history is Like Reality, Unless Noted). At best, these are actual people attending these ceremonies via remote viewing for their own safety, since episode 10 also hints that living in a giant cleanroom has lead to useless immune systems. For more likely, these holograms are all but completely automated, and every non-caretaker adult the Parasites see is a hollow shell used to create the illusion of respect and maintain morale.

The adults that the children are serving under are a rogue faction and that the rest of humanity are working with the Klaxosaurs because they are helping them rescue their children from the rogue's grasps.

Its unknown how Zero-Two was there but she's most likely kidnapped from her parents by Dr Franxx and this rogue faction of humanity who have Fantastic Racism against extraterrestrial life. Hiro and his friends are not Klaxosaurs but also children obtained through slave trading. Hiro and the others are used as hostages to prevent an all out assault. The 'true' humanity bargained with the Klaxosaurs with their assistance if they helped bring back their children and they will do the same for them.

Parasites have preprogrammed demises

When Squad 13 met Plantations 26's pilots in Episode 5, they reacted oddly to Zorome's question about Parasites becoming adults. At first blush, it looked like Parasites simply don't live to an old age due to how dangerous being a Franxx's pilot is, but certain hints indicate that they might in face be made to die before reaching adulthood.
One of them is the team leader of Plantations 13's Parasites (Code 090). Between his appearances in Episode 5 and 15, his hair has gone from dark to entirely white. I'm not sure how much time has passed in those 10 episodes, but it doesn't look like more than a couple of months. Then, in Episode 16, Zero Two accidentally discovered that Miku's hair has started to go white, but took take to not draw others' attention to it.
The simplest explanation for this is that Parasites are meant to die before reaching adulthood either by a result of the medical treatments they go through to be able to pilot a Franxx, or even by design as a way to make easier to create the sort of self-sacrificing mentality that Tyke Bombs like them are meant to have according to the top brass (think Protocol 32 from Episode 15).
If this is true, then all the above would be meant to be common knowledge among Parasites, but the main characters with the possible exception of Zero Two have been deliberately kept Locked Out of the Loop for reasons yet to be revealed, although most likely it's got less to do with sparing them the Awful Truth and a lot more with the Pragmatic Villainy and For Science! tropes.

• Another explanation might be that it's not Rapid Aging but a metamorphosis the parasite undergoes as their yellow blood-cells transform them into klaxosaurs, and they either die before the change is complete or being sent far away on a shuttle to complete the transformation in order to be propaganda fodder for APE to be used as combat practice for the new parasites. The reason nobody knows about any adult pilots, is due to all of them being sent of and vanishing akin to how children vanished while in the Garden. Nobody simply know, with the exception of APE, that is.

Magma Energy is Mako Energy

As in the very Life Energy of the planet, whose exploitation caused the Gaia's Lament scenario the world is currently in. Klaxosaurs are a form of Gaia's Vengeance that tracks down and destroy wherever the Magma Energy is being extracted the most, much like blood cells closing up an open wound and killing any pathogen that may infect it.

Franxx Theories

Thinking about another girl breaks the connection for piloting a FranXX

In Episode 2, both Hiro and Zorome's connections fell apart the moment they thought about someone other than their current partner.

• Jossed. This is a symptom, not a cause. While certainly a distraction, it's repeatedly shown that wandering thoughts on their own aren't enough to desynchronize. In particular, Hiro can pilot with Ichigo while thinking of nothing but Zero Two, once Ichigo accepts this fact on her end.

The controls on a Pistil's suit are a Magic Feather

As the series goes on, it's eventually revealed that Yellow Blood Cells bestow low-level Psychic Powers that are an absolute requirement in order to pilot. When a Pistil leaves her body to synchronize with a FranXX, she's not responding to her suit's control yoke (which looks incredibly simple for the commands it seems able to communicate), but psychic impulses generated by the Stamen as they use these controls. The reason for this is twofold - using fake levels makes it easier to train young Parasites than attempting to consciously nurture psychic abilities, and it's much more impersonal, better fitting APE/VIRM and their intention for the children to remain disposable, personality-free blank slates with no human connections.

Ending Theories

Society is going to disapprove of Hiro and Zero's Partnership.

• Possible endgame theory, or Grand Finale, so theory with caution.
• Potentially motivated by Hiro getting Injured, the city/command/the other pilots/everyone decide that Zero Two and Hiro's Partnerships is immoral, or "Wrong." (We have already seen that command doesn't approve of Zero Two)
  • Theory A: They will run away together like Zero Two has always wanted, flying off happily into the sunset.
  • Theory B: They 'Break Up,' with Hiro unwilling to go against Society, prompting a Downer Ending.
  • Theory C: Kittens
  • Theory D: They'll rebel against the command and stand a neutral ground, eventually bringing peace back and creating a new, free government à la "Lion King 2".
• Jossed as of the finale.

Zero Two will die.

• EVERYONE IS THINKING IT! DON'T BLAME THE PAGE!
• Zero Two only fights because she wants to Pilot with her Darling, having lost faith in the City long ago (possible motivation for this lack of care, "the City doesn't care about the Parasites/Pilots"). While Hiro still holds faith in the city, and wants do what he was 'Born?' to do. Fight the Klaxosaurs. However during the fighting, Zero Two dies.
  • For ultimate Tear Jerker, "Hiro will give Zero Two a Name" right before she dies.
• Also they go to the Front Lines at Hiro's motivation, while Zero Two just wants to runaway, Hiro insists they stay to fight.
• Alternately Zero Two will die, but it's long after the end of the series. Hiro's narration is him telling his kids the story of their mother and how they met. The bits that Hiro wasn't there for are him embellishing for the sake of making the story flow. Some of the more embarrassing or weird traits the other pilots have are in there because Zero Two was a troll all the way to the end and asked Hiro to exaggerate them so she could have something to laugh at from the afterlife.
• Confirmed. See the "Hiro and Zero Two will die together" theory for details.

Hiro will die

• Let's face it, he's also a dead man walking.
• Aside from the fact that anyone who pilots with 002 three times dies, there's also a metafictional reason. Zero-Two never shows grief for the death of comrade and has no concern for her allies. It would show key character growth for her to understand grief. And to have her realistically begin to understand it, someone she loves must die. And literally the only character who she truly cares about? Hiro.
• Confirmed. See the "Hiro and Zero Two will die together" theory for details.

Hiro and Zero Two will die together.

• Bread, Eggs, Breaded Eggs? Perhaps. However, in line with Episode 15's title, the two are each other's wings. In other words, it's pretty clear that having one die on another would go against the theme of the story, leaving the couple's fate to two options: live together or die together. There are a few reasons why the latter seems to have lower odds. 1. The writers and storyboard crew have previous experience creating bittersweet endings for couples at Gainax and Trigger. There's no reason to believe they couldn't do the same here. 2. Defeating APE will give humanity an opportunity to recover. Such a final battle, however, would put the two in grave danger. My guess? Mirroring Episode 13, Zero Two will be captured and experimented on by Papa's goons, this time to the point of making her Healing Factor stop working. Hiro, however, will save her and kill Papa... but not before he gets mortally wounded in the fight. 3. As a child, Hiro made a promise with Zero Two to marry her and take her to the outside world. I'm guessing that, just like Nia, the two will barely hang on and marry before going out to the outside world. That outside world would be the afterlife...
• CONFIRMED IN EPISODE 24. In their final fight against the VIRM, the two break away from Sterilizia True Apus to form a Golden Super Mode of Sterilizia and then form a lance out of pure energy to dive themselves into the Klaxosaur bomb. They finally defeated the VIRM, but it came at the cost of their lives. It's heavily implied that the two have reincarnated as human children at the end, but it doesn't change the fact that our Official Couple met their ends together. Goddamn it...

The epilogue will homage Cross Ange's Epilogue

By that I mean: Plantation 13, regardless if Hiro and Zero Two are alive or not, will likely earn their happy endings alongside the now-allies Klaxosaurs, while the adults have to survive by themselves.

• The fact that the Klaxosaurs are the true Lesser of Two Evils reinforce the theory. Now if now the Klaxosaur Princess could join forces with the Plantation 13...
• But more important... if Hiro and Zero Two are alive, they can have their own cafe!
• Partially confirmed. Plantation 13 earned their happy ending, as we see Mitsuru and Kokoro raising their family, Ichigo carrying Goro's child, Ikuno and Naomi alive and together, and Futoshi running his own bakery. Unfortunately, with Klaxosaur Princess, Hiro, and Zero Two all dead and the Klaxosaurs fusing to the earth, we probably won't be seeing Plantation 13 living alongside the Klaxosaurs anytime soon.

The final couples:

• Hiro and Zero Two
• Mitsuru and Kokoro
• Zorome and Miku
• Ichigo and Ikuno
• Goro and Futoshi (what!?)
• Final tally as of the finale:
  • Confirmed: Hiro and Zero Two, Mitsuru and Kokoro
  • Jossed: Ichigo and Ikuno (Ikuno ends up with Naomi), Goro and Futoshi (Goro ends up with Ichigo; Futoshi is unknown but has children and a bakery to boot).

Naomi will appear again

If she is not dead, at least. Then she'll die again in the last episodes.

• The first half is confirmed, Naomi returns on episode 22. The second half is jossed. She lives to rebuild society, and is implied to be romantically involved with Ikuno.

The ending will pay homage to GunBuster

Hiro and Zero two will successfully be able to end the VIRM menace once and for all, however they wont be able to get back through the warp gate. Instead, they'll end up going at faster than light speed, with time dilation making them arrive back on Earth thousands of years in the future — to a now recovered planet that has been waiting for their return (and where klaxo sapiens and homo sapiens live together).

• Confirmed. The cherry blossom tree that grew from the ashes of Zero Two's body became a beacon that called Hiro's and Zero Two's souls back to Earth centuries after the final battle.

Other Theories

The "infection" surrounding the parasites isn't anything physical, it's possessing normal human attachments.

From episode 10, what do we know about the adults? They don't understand romantic or familial love, they gain happiness from artificial means] rather than the normal human measures, are antisocial to the point of finding conversation exhausting, and dismiss marriage as inconvenient. Now compare that to our protagonists, who's emotional interactions drive most of the plot...and are called "infected children." It's marked as the reason group 13 is unusual, which indicated it's not normal among the populace.

Alpha Two is the equivalent of Evangelion's Kaworu Nagisa

Sure, why not?

• Especially considering that: If the theory that the Klaxosaurs are mutated humans are right, Alpha Two is a human who can turn into a Klaxosaur by his own will, in a way not unlike Cross Ange's DRAGONS.
• But independent that he is a human or not, Alpha Two is a Hidden Agenda Villain.

The Nines (except Zero Two) are genderless or intersex.

They're much more androgynous in appearance than the other squads and everybody wears the same suit. At least in Japanese, I don't think they've been referred to by any particular gender. This is why they have "female" stamens and "male" pistils. They can probably switch positions whenever they want. Sorry, Ikuno.

Confirmed

Damage to the Franxx harms the girl, not the boy.

It makes sense. The expressions and dialogue for the robot usually come from the girl. Notably, when Zorome and Miku's robot gets knocked out, it's Miku who feels the brunt of it, and Zorome is not the worse for wear.

• Also, one of the 26th's partners died: the male survived while the female was the one who died. It's possible that the Franxx was critically injured, causing the death of the pistil.
• Manga Chapter 4 demonstrates that all feedback from accessing FRANXX go through the female partner only as her consciousness is temporarily transferred to the machine so when the male is having a conversation with the female, they are actually talking to the machine itself which appear on the screen rather than the person right in front of them. It's only rational to think that any sustained damage to the machine would have the effect transferred directly to the females rather than the males.
• This would also explain where the surplus of stamens to pilot with zero two came from
• This is outright stated to be true in episode 8.

The average adult in this society does not understand human affection.

They reason the adult don't explain kissing to them is because they don't truly understand the concept themselves: they have linked it to the purely pragmatic function of trading magma instead. Likewise, no-one in-series sees anything odd about the Franxx because they don't understand sex or attraction either, and therefore do not understand the Visual Innuendo of the mecha either. Some of them do understand,(Dr. Franxx, Nana) and deliberately segregate the Parasites so they can develop an understanding of it and can pilot Franxx better.

• As of episode 10, confirmed.
• Episode 13 implies that it's the injections given to the people cause them to lose their connections to the emotions with people, as some of the kids had already lost emotions from getting their shots since their days in Garden. This is somewhat strengthened by the scene in Episode 10 where the male partner had spent years away from his own female partner because the injections in his pod is a much better alternative.

Papa and his council operate from a space station in orbit over Earth.

During the Klaxosaur attack in the first episode, Papa's image glitched out, suggesting that he (and probably the rest of his council) were using telepresence via hologram for the opening ceremony. Thematically, it makes a good deal of sense for the leadership of this society to live their lives high above the world over which they preside, safely out of reach of environmental turmoil and klaxosaur attacks.

• If the Plantation 13 parasites do end up rebelling against APE, an assault on a space station would fit nicely with Studio Trigger's tradition for high-altitude/spaceborne final battles.
• Confirmed.

Pistil-pistil piloting (and perhaps even stamen-stamen) is possible; Ichigo simply had an Incompatible Orientation for the test with Ikuno to work.

Despite not meeting the minimum requirement, Ichigo and Ikuno did have non-zero pulse values during the test, suggesting that a female pilot can provide the masculine energy required for activating a Franxx.

• Semi-confirmed with the Nines, who have some male Pistil/female Stamen pairs.
• Fully confirmed in Episode 23. Given Zero Two's catatonic state, Hiro is shown piloting a Franxx with Nine Alpha (a partial clone of Zero Two).

Zero Two is a "queen bee".

Before you can ask yourself "what the heck does that even mean", hear me out.

• The entire show runs on floral themes and which animal is extremely connected to flowers? The bee.
• Queen bees are different from worker bees: they're stronger, sexually mature and have different eating patterns because of a difference in diet. Rings any bell?
• This ties in with the theory above; queen bees are created by feeding normal bees with this thing called royal jelly, which is basically a diet exclusive to them. Now, assuming piloting with Zero Two is like being fed royal jelly, who do we know that as of episode 5 has started to try out the things she likes to eat? Oh, hi darling!
• Her honey obsession. We were all thinking it, don't deny.
• In a bee colony, drones (male bees) die after mating with the Queen Bee. Zero Two is known as the "Partner Killer." *Observes the stamen and pistils in the Franxx. Coincidence?
• Episode 12 confirms this. Piloting with Zero Two is making both her and Hiro gain more klaxosaur traits.
• Episode 13 hints that Hiro taking in Zero Two's blood during childhood may have some implication to the changes he's experiencing

Hiro already named Zero Two.

Episode 12 reveals that Hiro had already met Zero Two before and was forced to forget about her for some reason. As a kid, he had a knack for naming the other children. So he might have named her too. What did he possibly name her? Honey.

• Reason One: She enjoys drowning her food in it. Either he named her because she likes it or she loves it because of him.
• Reason Two: It goes with how she prefers calling him "darling" over "Hiro". Both names are a sign of affection.
• Reason Three: She hates that she's a monster. If Hiro went by his usual naming scheme, she would be called "Oni". Since they know about the mythical Jian bird, they may also know about the Japanese ogre. Her name would make her more of a monster.
• Reason Four: The katakana for Honey is ハニー, which retains the symbol for 2 in it from her code number. It also has a 1, which could be interpreted as the 1 from Hiro's code number.
• Confirmed in Episode 13. Zero Two is Hiro's nickname given to her when they met as children.

Zero Two will not be able to use the stamens she was given to fight in the Gran Crevasse.

Because of her experiences in the battle from episode 12/13 and Hiro's words to her in his hospital room, she lost the will to connect to and drain stamens like she did previously. She might have FRANXX connection issues with them, or she might make the decision to abstain from them. Either way, she'll be forced to pilot alone.

• Confirmed in Episode 15, but not for the reasons stated above. Zero Two is seen piloting the Strelizia in Stampede Mode because she had consumed all the Stamens beforehand.

Hiro will be much harder to control moving forward

Young Hiro was a constant benevolent menace to the staff, with his inquisitive attitude and willingness to cross lines. This behavior only stopped when his memory was erased, and now that's been reversed - and not just his memories of Zero Two, he remembered his promise to Mitsuru (which Zero Two couldn't have known about), suggesting his entire previous attitude has been restored. His escape from the hospital and stealth run back to the birdcage is already evidence of this. He's Back!, and once he moves through his Heroic BSoD, he's about to start burning the rulebook.

• Confirmed in episode 15 that this is exactly what he intends to do, now that he has his memories back.

Hiro is also somehow related to the Klaxosaurus.

• He's been considered the odd one out since episode 1, Zero Two feels a connection with him as soon as she spots him and he's the only one who isn't affected by the aging curse she seems to inflict on her partners (come episode 5, we learn that piloting with her has the opposite effect on him). They're also the only two people so far to sport that particular eye color, which isn't saying much since everyone in this anime has weird hair and weirder eye colors, but that may be a clue.
  • Alternatively, piloting with Zero Two will somehow make him gain Klaxosaur traits. Since she chose him, she might be trying to make him stronger and the nightmare-ish growth on his chest could be the beginning of some kind of mutation.
  • This is possible, seeing that the Klaxosaur core seems to be blue similar to Hiro's own cancer-ish growth. It's possible that the the core will develop around a host and that develops into some variant of Klaxosaur.
• Confirmed in Episode 12. Both Hiro and Zero Two are undergoing a process called "saurification" that is making them gain more pronounced klaxosaur traits. Hiro's klaxosaur cells are more concentrated in the left side of his body, where the growth was.
• Episode 13 kind of hints that his change began since childhood because he actually took in Zero Two's blood when he was treating her injury by licking on it
• Further reinforced as of the Episode 17 finale. He's growing horns.

The girl at the end of Episode 16.

We see a shot of someone who looks a lot like Zero Two, only with darker skin. There are many answers to what she could be. A prototype, a failed experiment. But more than anything there's something she is almost definitely. She is code 001.

• Confirmed in Episode 17's credits.

The reason Ikuno and Mitsuru have trouble connecting together is one (or both) is gay.

• Mitsuru's hero worship of Hiro, and strong turn against him when he fell off the pedestal might hint at a more serious attraction.
• Ikuno being lesbian would explain her low sync numbers with Mitsuru.
  • Some support for this: Ikuno is always stealing glances at Ichigo in the background, and blushed when Ichigo touched her shoulder in episode 4. Then she touched the same shoulder herself before connecting more strongly than before.
  • In episode 5 after Miku starts a conversation about how good-looking the boys from Plantation 26 were, Ikuno dryly remarks that she "has no interest in such things".
• Episode 11 tells that Mitsuru's case is more psychological rather than sex-oriented as his "broken promise" is what closes his heart to others. Ikuno's reactions in Episode 11, however, may really be a call sign of her being a lesbian.
• Confirmed in Episode 18. Ikuno is revealed to be a lesbian and she confesses her feelings for Ichigo.

Teenagers are used for piloting FranXX because their libido has just awakened at this age and is overflowing.

The Parasites are taught nothing about their sexuality or romance, yet the positions of the Stamen and Pistil and the feelings that they get when they pilot are very reminiscent of sex. And there's some secret about what happens to Parasites when they become adults. So it could be that the FranXX are powered by libido. And because libido cools down as you get older, the Parasites are disposed of when they get too old.And the reason romance and sexuality aren't explained to the Parasites is because of how powerful and uncontrollable it can make them. Zero Two is aware of what romance is, and she's a loose cannon who currently has no regard for anyone except the guy she picked as her "darling".

• Confirmed: Sort of, episode 19 shows that working reproductive functions are necessary for FranXX to work.

One possible application of magma energy technology is immortality.

Dr. Franxx, by no means a young man, calls Papa's council "geezers". Perhaps they've been in charge for actual centuries.

• Probably not centuries — the abandoned coastal town could only be abandoned for at most decades, not even a single century.
• Confirmed.

The Magma isn't actual "magma" from the planet's core, but "klaxosaur oil".

It's the mineral oil, composed by fossilized klaxosaurs from the far distant past, and if the theory of klaxosaurs being humans is correct, then it's the liquefied form of humanity's history and ancestry as well, mixed with something that introduced the "yellow blood-cells" into the planet's system. There might be no real "black oil" left in this world, depleted, hence the need for a new source of fuel for APE's usage, while the klaxosaurs themselves only want to preserve and protect it. Also would explain why the klaxosaurs are so hellbent on retrieving it, as APE would be practically robbing the graves of the Klaxosaur ancestors in order to fuel their own lifestyle. No wonder the klaxosaurs would be pissed off with them.

• Confirmed in Episode 20. The Magma isn't actual magma at all, but rather substance derived from klaxosaurs who “returned to energy”.

"Magma Energy" isn't really molten rock

Rather, something else that APE calls Magma Energy is being used to power the Plantations and everything else in the series.

• Confirmed.

The Klaxosaurs and the Franxx are related.

• Looking at Strelizia's "stampede mode" it wouldn't be too far fetched to think that the Franxx are nothing but modified klaxosaurs (or, alternatively, that Dr. Franxx created them using klaxosaur cells). The children control them from the inside and refrain them from going out of control. That's why they're called "Parasites": they invade and conquer.
  • The show being full of Neon Genesis Evangelion references, it would tie in nicely with the Evas being created from the Angels' DNA.
• Confirmed in Episode 20.

Zero Two's hairband is some sort of Restraining Bolt/Emotion Suppression device

In Episode 5, right after Ichigo slapped Zero Two and the latter's hairband fell off, a little LED-like light on it can be seen flicking off for a moment, revealing that it is more than a simple hairband. Then Zero Two immediately goes full Red Eyes, Take Warning/Game Face and seems ready to attack Ichigo when the sudden rain stops/distracts her.

• This is definitely possible since in the first episode, despite not wearing the headband for a while, she seems perfectly in control around Hiro because she doesn't see him as a threat. While with Ichigo, who Zero Two sees as an enemy/nuisance, the red eyes serve as some sort of defense mechanism to scare others away, kind of like animals do when they push their fur out to appear bigger.
• Episode 13 tells that she got infuriated back when Ichigo's comment of her being a monster is because Zero wanted to become as human as possible because of her experience with Hiro during childhood runaway and the story which was told in the picture book, thinking that her only way to be with Hiro is to become human and calling her a monster reminds her that she is actually not human.
• Confirmed in Episode 21. Not long after it breaks, Zero Two reverts to her original Klaxo Sapien form.

Dr. FranXX will undergo a Redemption Arc of sorts

And it will start with him restoring Kokoro's and Mitsuru's memories. It's likely that on some level he feels horrible for his hand in creating the world ruled by APE. Once he learns of Kokoro's desire to become a mother, the same way his first love felt, he'll restore their memories and help the Plantation 13 parasites stage a rebellion. Note that I said "Redemption", not a Heel–Face Turn. He still an amoral guy for what he did to Zero Two as a kid in his quest to create a perfect life form.

• More like a Redemption Episode, but Episode 21 confirms this.

Jossed

The setting is on a planet or moon with a lower gravity than Earth's.

Note the way that Hiro goes flying after Zero Two when she pulls him into Strelitzia, and the remarkably long, soaring jump she makes when confronting Hachi and Nana in Episode 3. The setting being a planetoid in the process of colonization would also explain the barren, lifeless exterior and the settlements being called Plantations.

• Somewhat explained in the manga as the explanation given is that the human beings got too greedy in harvesting Magma Energy that all the subsequent actions destroyed the planet ecology system, rendering the planet surface barren and basically inhabitable and all the leftover humans have to resort to living in the mobile fortresses though there's no mention of what planet that is. However, seeing as how the manga emphasizes on the destruction of ecology system, it's likely Earth or some place very much like Earth. The harvesting itself may have caused some sort of disturbance to the planetary gravity
• Jossed by episode 6, showing ruins of a couple of skyscrapers.
• Episode 7 gave us a clearer picture when the group stumbled across a long abandoned town. There are Japanese characters found at certain places, with one English word appearing on the glass entrance of a shop at the scene where Zero surprised Ichigo from behind, pretty much confirming the planet where the entire setting takes place is on Earth.

Hiro will give Zero Two a Name

• Not a surprising WMG of course, but it won't be the obvious 'Oni' mentioned elsewhere. Instead, he'll take it from her favorite food, and slightly modify the pronunciation, and go with Ho-Ni (Honey). It'd also match with the name she gave him: many couples call each other "darling" or "honey".
  • Episode 4 had Hiro deliver what was basically an Anguished Declarationof Love. Assuming that he ends up being the one to break her curse of killing every co-pilot she's had so far (something that will likely happen, considering a), the show is confirmed to run for 24 episodes, and b), if they were going to drag that sort of thing out, they wouldn't have had him pilot with her a second time), it could be that this ends up being a Relationship Upgrade for the two (except they won't know about it, since they haven't been taught about love).
• Jossed he won't because he gave her one when they were kids as Episode 13 shows. It's Zero Two.
• Wouldn't stop Hiro from giving her another one as he himself considered Zero Two as lousy name though he initially came up with Oni during the first attempt

Zorome is transgender.

• Okay, yes, I know, given everything we know about this setting this seems very unlikely, but hear me out.
  • Zorome's the smallest of the male cast and is voiced by a woman. He uses the super masculine ore-sama. He's constantly trying to assert how awesome and strong he is. He man-spreads to a degree that has to necessitate actual effort. The "short guy who wants to be macho" is a common archetype, but there's two more things:
  • In Episode 5 he's the one who's extremely adamant about the separation between the boys and girls, and- very important- looks disgusted at the fact that Futoshi would willingly sit with the girls.
  • In Episode 2, he wears this sports bra looking undershirt thing◊ that, from what I can tell, the other boys don't seem to wear... but the girls do.◊
  • Given how rigid the setting is about gender roles it feels like it wouldn't be unfitting to have characters that might challenge that.
• Jossed in episode 7, where we see him shirtless.

Hiro is a clone of the original Hiro

I kinda believe that the Hiro were are seeing is the clone of the original. The original Hiro died long ago and Zero Two is unable to join him as she is immortal. She wants to become human, a mortal being so she could die and reunite with the original Hiro.

• Jossed.

Ichigo will turn heel.

Ichigo will not at all be impressed once she finds out Hiro won't reciprocate her feelings, especially if Episode 13 was anything to go by. Something is telling me she's going to sabotage Hiro and Zero Two, cementing herself as an antagonist...

• Maybe this will finally give Hiro a chance to make amends with Mitsuru - he'll have to pilot one of the FranXX to take Ichigo down, but Mitsuru will be the only one nearby who's available as a partner (either the rest of the pilots refuse to pilot with Hiro, or Ichigo incapacitates them), and Mitsuru, touched that Hiro kept his promise (even if unintentionally), has a Heel Realization, and starts treating Hiro better.
• Jossed. She sure as hell doesn't like losing, but piloting with Hiro and seeing his head full of nothing but Zero Two finally convinced her to step aside peacefully.

APE are a Hive Mind.

They are basically a alien AI with separate functions and purposes serving as their council, which would explain their We Have Reserves mindset , their lack of interest in individuality in the parasites, humans and robots, and why they don't seem bothered with losing two of their own council as casualties to the klaxosaurs and how they know these two had perished despite being no survivors of the envoy to report back to them. They simply can't tell the difference between physical and mental existence, allowing them to discard the physical aspect of bodies as a optional choice. It's also why they assign numbers to their human stock, since as a AI, numbers are far easier to comprehend than actual names. In this case, even destroying the council wouldn't stop APE's existence, as long their core remains intact, (maybe stashed away at the space station they inhabit.) And speaking of this theory...

• Jossed, they're not.
• Partly Jossed/ Partly confirmed. Papa and the Vice Chairman are actually part of a Hive Mind... and also an alien one on top of that.

Dr. Franxx created APE.

As the lone human member of the council, the idea of a AI- Hive Mind accepting a mind that isn't part of them would come of as illogical, unless the human mind in creation is their creator. DR.Franxx have cyborg implants and lived for the whole century that the klaxosaur war has lasted and displayed multiple true human traits, (such as perversion, the understanding of emotions and their importance and the like.) Hinting he might be from a time before the whole mess started. the fact that they allow him to try new options such as the Plantation 13 squad shows that the doctor do have a lot of pull within the Council, which wouldn't be granted to a ordinary human expert in the area. For some reason in the past, he created the council of APE and joined in since the potential scientific path intrigued him. However, upon seeing the stagnation of the human race that APE's choices created, he decided to start undoing the damage of his creation by reverting humanity back to its roots, starting with a new team of parasites, before the damage that APE does become irreversible.

• Jossed, he didn't.

Klaxosaurs are man made

After the reveal that there was a human-like body in a core, there's a chance they were created by APE to extract the magma before things went bad.

• Jossed. They are biological weapons piloted by klaxo sapiens, and operate similarly to that of Franxx mechs (the stamen being the yellow cores, the pistil the Klaxosaur itself).

Papa and Co are robots

We already know cyborgs are a thing in this universe (Dr. Franxx), and we've never seen their skin. Between that and the general cold nature of all adults in the series makes one wonder.

• Jossed. They're members of a hostile alien race known as VIRM.

Papa isn't real.

He's an in-universe fictional person who is "performed" by various people to serve as a figurehead idol to control the devotion of the parasites and average citizens.

• Jossed. He is the same Papa the whole time.

Strelizia's episode 15 Stampede Mode

Strelizia wasn't in stampede mode because Zero Two devoured all those stamens. Instead, she refused to have any Stamens at all, in keeping with her saving other FranXX in the battle, she refused to kill anyone else for her piloting. Hiro's comments got to her and she's changing her attitude.

• Jossed. She ate them all.

The Klaxosaurs are actually humans.

• And they're from Another Dimension.
• Or, they can be Human Aliens.
• Given that Zero Two is a Half-Human Hybrid, the theory is plausible.
• The "Parasites" or Pilots are actually Klaxosurs, Zero Two is the original Human bread copy, and Klaxosaurs are just Corrupted Franxx.
  • As the Franxx are meant to symbolise sex, Klaxosaurs are to represent STDs.
• They do have human-shaped objects in their cores...
• Jossed in Episode 20. They're the female descendants of Klaxo-Sapiens.

Zorome will pull a Face–Heel Turn.

Think about it, his codename invokes the Number of the Beast. And he is one of the characters (The other being Mitsuru) which is not pleasant.

• Episode 3 shows that despite his antagonism with Hiro, he seems to care for Miku.
• I think that his Face–Heel Turn will be motivated for love rather than his own Pride.
• Alternatively, his betrayal will be motivated for both love and pride.
  • Episode 5 puts a spanner in this theory, since he's more than happy to work with Hiro when the latter calls a truce. If anything, Mitsuru seems more likely to do so out of jealousy towards Hiro.
• Jossed. He stays loyal to Plantation 13 and becomes a teacher with Miku after the series finale's timeskip.

Ichigo is going to lose an eye.

Episode 7's ending sequence has a shot◊ of Ichigo holding a red hibiscus flower over her right eye. The flower's color and ragged edges are more than a little evocative of a bloody wound.

• Jossed.

Hiro is not immune.

Episode 4's closing narration says that flying with 02 will slowly destroy him. He may be right. It's just his honest desire to fly/pilot with her is stopping her from doing to him what she did to Mitsuru. Eventually, they'll encounter someone they *have* to go all out against which will destroy him.

• All but confirmed in episode 5, though apparently piloting with Zero Two causes him to develop an illness opposite to the one all her previous partners had.
• Episode 13 puts this up for debate as Hiro was shown to have taken in some amount of Zero Two's blood during childhood, hinting that he may have developed some sort of immunity system towards the change over the years whereas the previous Zero Two's partners were all subjected to the change abruptly from the first day they started piloting with Zero Two, straining their bodies to the point of breaking.
• Jossed. Because he licked Zero Two's blood during childhood, he not only becomes immune to Zero Two's three rides rule, but also gradually transforms into a Klaxo-Sapien hybrid.

Zero Two's new name will be Sakura

The other parasites' names are plays on their code numbers. So how could Zero Two get a different name from the rest? The answer is multi-pronged.

• As seen in the 2nd OP as well as Episodes 1 and 16, cherry blossom petals have become a recurring symbol in the show. In Japan, cherry blossoms symbolize the cycle of life, death, and rebirth. Zero Two would perfectly represent its symbolism if she dies but is then reborn thanks to her Healing Factor, so Sakura would be a great choice for a new name.
• In Episode 13, Hiro admitted that Zero Two wasn't the best name he could've come up with. So while he has technically already named her, what's to stop him from giving her another name?
• Such a moment will likely come in the finale, probably not long after APE's and/or the Big Bad's final defeat. In this case, children would likely no longer have code numbers for identification. What would be a better way to present a brighter future than to have a character like Zero Two obtain a name that has absolutely nothing to do with APE's code numbers?
• Jossed... at least for the original Zero Two, since she dies with Hiro in Episode 24. Interestingly enough, however, it's revealed that she and Hiro get reincarnated as fully human children. The two are also seen playing under a cherry blossom tree.

Zero Two will call Hiro by name rather than Darling.

• All that's left to answer is how and when. It could be as menial as a slip of the tongue, or it could be a dramatic Say My Name during battle.
• Episode 13 shook this real hard as it's shown with a very likely implication that she keeps calling him Darling is because Hiro suggested it during their runaway attempt when they were young. Whether that will change to calling his name is not entirely cut off for now.
• Jossed as of the finale.

Hiro is a direct clone of Papa.

So I was rewatching episode 1 and I noticed how, right after the opening scene with that red, demonic looking lady being attacked by a horde of Klaxosaurs, there's a cut to Zero Two and someone who looks a lot like Hiro from the back walking side by side. Only, I noticed Zero Two's uniform is not the usual red, but a grey much more similar to the ones the Parasites wear. Now, if that scene was a flashback in her mind, it might be possible that she and Papa were the original pilots, but the aging curse she inflicts on her partners had its effects on him and forced to jump from Stamen to Stamen to keep fighting. If they were the best fighters and she "crippled" him, it'd make sense why everyone considers Zero Two such a problem, not only for her Klaxosaur blood.

• When she spots Hiro for the first time, Zero Two says "Found one!". She may be talking about spotting one of the Parasites, but what if she recognized him because of his features? If her code is 002, someone must have had Code 001, someone strong enough to pilot with the resident Loose Cannon.
• Before losing his abilities, Hiro was a prodigy in the Franxx, someone you heard about even in other Plantations (much like a God-like figure the kids pray to even before eating). After he pilots Strelitzia, it's said Papa will give special orders to deal with his situation. Simple precautions, or something more?
• Episode 7 tells us that Hiro got dragged into the spotlight because of Zero Two as he's a "prospective partner" for her. It's when he's shown to be able to bring out her potential, all the adults decide that he should be put under close surveillance, along with Zero Two herself for a yet unknown reason.
• Episode 11 kinds of hint at something sinister when we watch the scene where Mitsuru's recollection of the past and the scene where Hiro asked about the "promise", his eyes are all blank and emotionless. If we take into consideration how Hiro was personally set by the higher ups to be on the team despite not having a partner to pilot a FRANXX, and the discussion that took place after Hiro pushed Strelizia past the normal limit after bouncing back from the brink of death... it's possible that Hiro may be one of the test subjects groomed to be Zero Two's partner at a very young age.
• Episode 13 throws everything into the grinder. Hiro is simply the lucky one. Also, the way Episode 13 is shown.. the scene where Zero Two spouted "Mitsukeda!" when she first saw Hiro should have been "Found you!"
• Jossed. Papa is revealed to be a member of the VIRM. Hiro transforms into a Klaxo-Sapien/Human hybrid, but starts off as a human.