The Public Safety uniforms being standard "office attire" seems like a unique quirk of the series until you realize that, as members of a Public Safety Bureau, Devil Hunters are supposed to dress like security guards.
If the Yakuza wanted the power of a Devil, then why didn’t they kill Denji and take Pochita? Possibly because they saw how close the two were and that if they killed Denji, Pochita would be none too pleased by what they did to allow them to use him at all. And it would likely result in all of their deaths at the hands of Pochita if they did kill Denji and try to take him.
Why is Denji's Starter Villain the Zombie Devil? Because chainsaws are often seen as an effective weapon in many media featuring zombies.
Kon the Fox Devil managing to kill the Leech Devil with a single hit seems very strange at first considering far more people are a scared of leeches then foxes. But taking into account that Kon has likely been eating other Devils at Public Safety’s behest for at least a few years, she’s likely far stronger than an incarnation of the Fox Devil could ever become naturally. This can also explain why she’s contracted to so many hunters at such a relatively small price: Kon seems to greatly enjoy eating other Devils, and working for the Bureau is the fastest way to get her claws on all the Devil meat she could ever want.
Denji boasts/taunts Aki on their first-meeting and dust-up in the alleyway that when he fights against dudes, he goes for the nut shots as often as possible. When he defeats Katana Man in their second fight, he does so by slicing him in half vertically with an upwards kick, using a chainsaw sprouted from his leg. Denji defeated his fiend form with a Groin Attack, and then tortured him in his human form with multiple ones. Katana Man is lucky the damage took a minute to effect his whole body, or he'd have felt the pain of a chainsaw blade to the scrotum.
When Santa asks for four children as the reward for killing Denji, he mentions that three of them are for contracts and one for pleasure. At first it's assumed he's a disgusting, dirty old man preying on children, but as the truth about him is revealed, it becomes clear that this child's purpose was different: knowing she would need to use her two perfect dolls for contracts with the Hell and Darkness devil in the coming operation, the Doll devil wanted to get her hands on a new child to groom and turn into a perfect doll. Not that it's a better fate...
One of the Darkness Devil's powers is the ability to remove the arms of its opponents without damaging their clothing. It seems rather oddly specific until one realises that one of the most common things people do to get their bearings in darkness is feel around with their hands.
When Pochita comes back as Chainsaw Man, he’s still possessing Denji’s human body. That makes him a Chainsaw Fiend, not the Chainsaw Devil. And Fiends are usually weaker than their Devil forms. Meaning Pochita was already weakened significantly and still gave Makima and the Hybrids such a Curb-Stomp Battle that Makima realized she had no chance against him in a fair fight.
It makes sense that Aki fights using a sword. His goal is to kill the Gun Devil, and in popular imagery guns are often contrasted with swords.
Aldo is seen aiming his gun with his left eye, despite being right-handed. While it's entirely possible for a non-leftie to have a dominant left eye, there's another potential explanation in his case: his right eye may have been injured during the incident which left him with scars over his eyebrow and eyelid, affecting his vision to some degree and forcing him to rely on his other eye for tasks requiring precision.
Of course the Chinese Quanxi would be the host of the Crossbow Devil. The weapon was first invented in China in the 7th century BC.
Everyone who called for help and got it from Chainsaw Man was immediately killed afterwards because they couldn’t survive being hugged, which was Chainsaw Man’s price for receiving his help. Kobeni called for help but didn’t have to hug or get hugged by Chainsaw Man in return. Why is that? Because at the time, Chainsaw Man had something else he wanted more than a hug. Fulfilling Denji’s dream of going on a date with a cute girl. So Kobeni was actually lucky at that time cause otherwise, she would have had to pay Chainsaw Man back with a hug and would have been sliced to pieces.
The War Devil can only turn what they believe belongs to them into weapons. Why is that? Many armies throughout history were basically the property of their governments and were used to fight their leader’s battles, regardless of how the soldiers felt about the war. The War Devil’s power is basically that on a smaller scale. Anyone who belongs to them is their weapon to be used to fight their battles.
Additionally, Yoru claims that a weapon made from one of Asa's belongings is stronger the more emotional attachment that she has to it. As the old saying goes, "All's fair in love and war". Love is often perceived as a conflict between two people when in the stages of developing romance, and causing someone to feel love for you is often denoted by feelings that someone has "fallen", along with a sense that they belong in some way to the person who they've developed feelings for.
It is also a reflection of the limit on Makima's ability as the Control Devil of only being able to dominate those who consider her superior. This might suggest that the Devils representing the Horsemen of the Apocalypse might have a common quality of their powers being defined by people's relation to them.
Additionally, the War Devil not being able to blend in with human society properly makes sense as war often leads to the breakdown of social order and mass chaos. So as the embodiment of war and all the chaos war brings, it makes sense that it doesn’t understand the orderly and structured way humans normally interact with each other.
By contrast, the Control and Famine Devils are considerably better at navigating human society than Yoru; as detailed below, Makima is The Social Expert who can skillfully manipulate people without even using her powers, and while we don't know yet how good Fami's social skills are, the fact that she went unnoticed until she approached Asa suggests she's at least competent enough to avoid suspicion. Control is a necessary component for society to function, and even though famine stresses the social order, it doesn't break it down to the degree war does.
Though much of her control over people surely stems from her use of her supernatural powers, Makima's first few interactions with almost every character she meets also work extremely well to establish just how good of a manipulator she is based purely on social skills. Namely, they demonstrate just how adeptly, in every situation, she's able to effortlessly understand each character's unique personality and switch her tactics to appeal exactly to them:
She seduces Denji sexually and offers him sympathy, a shoulder to cry on, and otherwise, the human warmth that she realizes how much he wants and never had.
When she wants to get Power to fight for her, she uses simple reverse psychology by implying that she's not brave or powerful enough - having realized in an instant that she's dealing with a simpleminded brute who'd see that as a challenge she can't refuse.
When she wants Aki to take Denij and Power-in, she convinces him by telling him that she chose him because he's her most reliable employee - using his need for validation and his secret insecurity.
When negotiating with the yakuza boss, she starts reasonable and diplomatic but doesn't bat an eyelash before revealing that she's tortured and disfigured his loved ones to threaten him into compliance the moment she realizes it isn't enough.
Explanations for the existence of Devils based on Absurd Phobias:
The Tomato Devil was likely born in the 1700s, when people died from poisoning after eating them on pewter plates. The acidity of the tomatoes caused the pewter's toxic lead to leach out and got consumed. As such, people thought that tomatoes were poisonous for decades, and this fear is likely why it's bigger and stronger than the Chicken Devil.
Another likely reason that the Tomato Devil is inspired by Attack of the Killer Tomatoes!, with its status as a parody horror film also makes it a joke in-universe.
The Marshmallow Devil could have been born when Ghostbusters (1984) was released and the Stay Puft Marshmallow Man became known to the public, a decade or so before Chainsaw Man's events take place.
The Stone Devil most likely came from one of the once-common punishments of stoning, in which a large group of people would throw many rocks at the individual, usually injuring or even killing them. Even in context, large stones can easily crush a person to death, given with real-life incidents of cave and structural collapses.
How did Makima so easily Curb-Stomp the Gun Devil? In real life, while being controlled by someone else is scary, it doesn't seem as threatening as a gun. But in the Chainsaw Man world, this fear is very real because anyone with authority over you can trade your life in a Deal with the Devil and there is nothing you can do about it.
The anime's seventh outro has the Gratuitous English of "Get get get on, get get get on, get on chu." However, "get on" sounds like "gero," which means "vomit." "Chu" means "kiss." So this song can be understood as "vomit kiss," aka when Himeno puked in Denji's mouth during their kiss.
Fiends and sympathetic Devils are usually given unique names than just "[Concept] Devil / Fiend." Devils are described as gaining power from the fear of their "name," i.e. the Chainsaw Devil is born from the fear of chainsaws. Makima's Fiends are not addressed by the name of their concept (Blood Devil / Fiend), but rather an entirely new name (Power). Devils allied with the Devil Hunters also have unique names, like Pochita, Prinzi, Angel (in the case of the Angel Devil, "Angel" can be and is used as a proper name), or Makima herself. This also includes Quanxi's Fiends, who have genuine love for their hybrid lover. Even the War Devil is given a unique name as a token of her (albeit strained) cooperation with Asa. These Devils and Fiends are more sympathetic or less powerful than Devils usually are likely, in part, because of this fact. It is also not unlikely that Makima gives her Fiends names as a form of control and subjugation.
The Famine Devil calls Yoru, the War Devil, her "little sister." Of course, humans have feared famine long before they have ever gone to war.
The Death Devil is the eldest Horseman, as all types of fears stem from a fundamental fear of dying. She may even be the oldest Devil.
Himeno having any lingering connection to the Ghost Devil after her death might seem odd, especially when another has summoned it. They didn't seem to have any interpersonal connection like Denji and Pochita and had a fairly standard Deal with the Devil that many members of the Public Safety do with various Devils. Until you remember that Himeno offered to "give you everything I've got" in exchange for the Ghost Devil's wholehearted combat efforts... apparently including her personality and will.
Also, it's the Ghost Devil. The embodiment of the lingering spirits of the dead. It's not that strange that it would still have some use for its dead contractors.
Of course there wouldn't be any more wars after "the great war" when Yoru got partially consumed by Chainsaw Man. It was probably World War I, a war so bloody that it's been dubbed as "the war to end all wars".
Why is the sword created from Asa's uniform so fragile despite its power? Because while it's a memento of Asa's deceased mother, it's ultimately just a easily replaceable school uniform that Asa will one day hang up when she graduates. The guilt of destroying it would be immense for only a moment and quickly fade.
Asa fighting the Falling Devil makes a lot of sense considering how many times she says that she tends to fall at the most important moments and how she trips and falls a lot.
Why does the Falling Devil seem to avoid unnecessary casualties, and even when taking body parts from humans seems to prefer only taking what she needs? She makes her dishes out of human flesh. If she just went around killing everyone in sight, she'd quickly run out of her primary ingredients. A good chef needs to be able to properly portion their supply of fresh ingredients after all.
Another possible reason for why the Falling Devil prefers to let other demons do the killing rather than herself? Well, it’s Not the Fall That Kills You…
Fami says her power is to control those who are starving. This makes sense as when one is truly starving, they'll do most anything to fill their bellies.
Of course nothing could possibly hurt the Falling Devil. The body she was controlling wasn't her true body, thus any damage done to it wouldn't affect her real body.
Yoru can largely be seen as a selfish reflection of Asa. While Asa has practically nonexistent self-esteem, Yoru is confident and self-assured. While Asa is constantly wracked by guilt for things completely out of her control (Such as her mother's death), Yoru is completely fine with taking lives or threatening others. While Asa puts way too much importance on what other people think, Yoru simply doesn't care about other people at all. They even share a number of personality flaws, such as immaturity and an unwillingness to take criticism. This ties into how, right before dying, Asa expressed a desire to live her life more selfishly. Yoru, at least symbolically, is that version of Asa made manifest.
Angel Devil claims that the last thing that Devils hear when they die in Hell is the sound of a chainsaw. While used mostly as a tree cutting tool now, chainsaws were originally invented as a medical tool to assist with childbirth. Which makes it fitting that, in their final moments before dying and being reborn, they hear the sound of a tool meant to help cut a way for a new life to be born anew.
Appropriately, the song Barem starts singing to himself right before starting his backup plan is Kumbaya, which is famous for being a campfire song.
Quite a few of the Fire Devil's unusual abilities make more sense given the attributes of what it represents.
It seems strange that the Fire Devil can give mind reading powers to its contractors but as Barem says, it gives its contractors the powers to transform into their ideal. Saying they’re making a contract with the Justice Devil means the contractor has already has an idea for what kind of power they want, which could be the power to read minds so they can enact justice.
And like fire, the power it gives is controllable at first but it can consume you the stronger it gets, as Yuko shows when she becomes more uncontrollable and dangerous the longer she stayed in her devil form.
The Fire Devil gets stronger the more contractors they have. Fire gets stronger the more fuel it has to burn and many fires starting in different locations also increases the difficulty in stopping it.
The fact that the main person responsible for spreading the Fire Devil contracts is the Flamethrower Hybrid.
Fire naturally changes shape and form, which is why a contract with the Fire Devil can transform the contractee. Additionally, what they transform to is what they desire; passion and desire is often associated with fire, i.e. the heat of passion, or the heat of the moment.
Why is Nail Fiend so obsessed with kids being in school and acting orderly? Because nails are designed to fix things in place and keep them stable. In other words: orderly.
Why did the Guillotine Devil defy Fami's orders to kill her enemies and only act as The Nudifier? One potential reason is that guillotines are primarily used in executions of people that have been condemned as guilty of a crime, and the guards Fami sicked it on didn't seem to have any direct involvement in the horrific actions their higher-ups performed on Denji, so it didn't see them as guilty enough to kill.
Chapter 132 ends up fueling fire to this: Denji seems to be under the impression that Yoshida wants sexual favors in return for Nayuta's safety. While funny at first, it becomes disturbing once you consider Denji's upbringing as a debt slave to the Yakuza and start wondering exactly why he'd assume sexually appeasing Yoshida would free him.
The body that became Power's is that of a young and beautiful teenage girl who was found dead in the woods. Make that of what you will.
And just imagine being one of that poor girl's loved ones. If they know she's dead and turned into a Fiend, then they likely have to deal with the emotional trauma of knowing that a Devil stole their loved one's corpse and is wearing it around like nothing's wrong. And if they don't know, they're likely worried about their "daughter"'s sudden shift in behaviour. And that's assuming they're even still alive...
It's clear that Santa Claus/Doll Woman has been making Perfect Dolls for a very long time considering that her latest puppet's grown into an old man. That begs the question: Just how many children has Santa Claus groomed into becoming a Perfect Doll?
Invoked when Santa Claus tells Denji that she had scattered dolls all around the world that could turn anyone into a doll with a single touch, taunting him with the horrific implications that anyone could turn into a doll and attack him.
Just about everything about the Chainsaw Devil's Abstract Eater ability:
For starters, we not only have no clue where such ability came from, as Chainsaw's the only being in the series to have it.
And that's not getting into the many concepts it has erased from reality. First Makima mentions Nazi Germany, World War II, AIDS, Nuclear Weapons and slow-onset asthma (SOA), which make sense since the setting is quite different from our world. Then Makima starts talking about things that don't exist (or we at least don't know exist) such as Arnolone syndrome and the eruption of Mount Hio. Then she starts talking about things that are plainly unthinkable, such as the human sixth sense, a star whose light broke children's minds and at least 4 end-of-life phenomena worse than DEATH ITSELF. Just what exactly is wrong about the world of this series?
The very possibility of this particular ability means that the Chainsaw Devil can literally rewrite reality to catastrophic results if he were to eat a devil that represented a concept that is not only feared but is essential for reality as we know it, let alone life. For example, were he to eat the Ocean Devil, Earth will not only become a barren and dry wasteland, it will always have been so. And if he ate the Fire Devil, then all fire and sources of it (up to and including stars) would have never existed, effectively destroying the universe.
Towards the end, it's revealed that the Chainsaw Devil is feared by all the Devils because when it eats a Devil, not only does it remove the Devil from the cycle of reincarnation it erases its concept from having ever existed. One of the concepts Makima mentions are nuclear weapons. And let's not forget that Devils gain power from people fearing the concept they represent; the Gun Devil caused untold death and destruction but imagine if there was a Nuclear Devil... Which became even more horrifying in Part 2 with Yoru's goal being to get it back.
Another piece of horror is the list isn't really in order, so the fact that Chainsaw Devil had to erase World War 2 and Nazi Germany separately means that either WW2 happened anyway without the Nazis... or the Nazis did something even worse in spite of WW2 never happening.
Considering before World War 2 breaks out in Europe, the Imperial Japan were already on warpath in China and Indochina, it's likely that if the Nazis were never existed, the war would likely focused on Asia Pacific theatre instead of Europe with Imperial Japan as the leading nation of the Axis rather than Nazi Germany.
Right before its nightmarishly one-sided “fight” with Public Safety, the Darkness Devil conjures a corridor of bisected astronauts praying to their own torsos in seeming mockery of humanity’s attempts to conquer their fear of the dark. Was that just an illusion... or are those the actual corpses of the brave souls who perished in the void? And if so, how did it get its claws on them?!
Considering that the manga takes place in an Alternate Universe, and Devils have existed alongside humans for who-knows-how-long, it's entirely possible that, rather than dying the way how they died in Real Life, that the Darkness Devil approached them while they were all in space, and took their corpses as trophies. Imagine the same fight Public Safety had with the Darkness Devil except with vulnerable astronauts trapped in the void of space with literally nowhere to run.
It is said that Darkness is so powerful, that it never experienced any form of death during its presumed millenia of existence. This is a very good thing, as if Darkness had somehow gotten killed in hell, it would re-spawn into the human world. One can only think the amount of damage it could cause to humanity before it could be defeated, if it could be defeated at all.
If the Horsemen of the Apocalypse are arranged similarly to the mythical ones, Makima was the weakest. What adds to this is that the Death Devil was confirmed to be the strongest Devil in existence.
Both of Denji's best friends and surrogate siblings were killed by guns, or at least something that looked like one. Frankly, it'd be a miracle if he doesn't have some sort of gun-related Trauma Button on top of the heaping pile of trauma that Makima inflicted on him already.
Also crosses into Fridge Brilliance, since Sword Man mentions the Chainsaw Man Church came to be by an absorbing a literal cult.
Humans under the contract of the fire devil were both already incredibly unstable yet powerful, so hearing that it only grows stronger and more uncontrollable the more humans make contracts with it is horrifying to say the least.
Taking into account Barem's jeer that cats and dogs are "more flammable", is very likely that, instead of "just" setting the condo ablaze and leaving the animals to their fate, he personally and directly burned Denji and Nayuta's pets alive. As if you needed more reason to hate the guy.
In Chapter 158, Fami revealed that her summons tend to be weaker than their actual power, as she demonstrated with the Guillotine Devil. Earlier, the Falling Devil was also summoned by her to motivate Asa... and her mere presence caused 2000 people to die due to gravitational ripple across the entire planet. Perhaps there is a very good reason why Falling Devil is supposed to herald the Apocalypse.
Imagine being Haruka: you've been manipulated into being the public face of a group that you believed aimed for world peace, only for the group to essentially perform a mass sacrifice of thousands of souls. Now you and your fellow students are the country's most wanted people alive because the real culprits behind the mass sacrifice used your position as "the face" to make you the fall guy.
Bordering on Plot Hole, why would the Angel Devil be retired just because his arms are missing? Shouldn't they have fed him blood so he could regenerate them?
Maybe Makima had a feeling he might squeal if she just let him go, so she decided to try and get rid of him under the cover of "retirement"?
that the eleven bisected astronauts are a reference to the number of astronauts (at the time the chapter was written) who have died on missions