The Outer Guardians watch over Hotaru as she continues to grow at an astonishing rate while also providing more information about the upcoming crisis. And after she fully matures into Sailor Saturn, she and her parents reunite with the Inners to unlock Sailor Moon's Eternal form.
Tropes in this episode include:
- All Your Powers Combined: At Saturn's insistence, the Sailor Guardians share their power with Sailor Moon which results in her Eternal form.
- Big Damn Reunion: Chibi-Usa is delighted to reunite with Hotaru and the feeling is mutual.
- Call-Back: Uranus calls the Inners "kittens" just like when they first met.
- Child Prodigy: Setsuna brings up how Hotaru has learned the theory of relativity and can recite sophisticated poetry.
- Existential Horror: Haruka recounts a science fiction story she read as a kid that describes how everyone in the universe is nothing more then a momentary blip by the will of an unseen creator. Michiru admits that the thought startles her.
- Failed a Spot Check: Haruka, Michiru, and Setsuna look for Hotaru in every part of the house leaving her room for last.
- Flashback Cut: Rei informs her friends on how she detected an evil aura coming from her shrine's sacred mirror.
- Flashback-Montage Realization: Hotaru is visited by her Guardian self who unlocks her memories from the Infinity Arc.
- Foreshadowing:
- After the commercial break, Mamoru is shown studying in his room in the middle of two portraits; one with a moon over a city and the other a building with a hellish color scheme. If one looks closely, Mamoru looks like he's closer to the second portrait.
- While talking with her friends about the strange anomalies going around, Minako brings up how she noticed lots of people staring at mirrors for long periods of time.
- Friendship Moment: After seeing their friend look blue while hanging out, the Inners encourage Usagi to talk about her recent problem with Mamoru.
- Getting Crap Past the Radar: Usagi suggests that she and Mamoru can do more "grown-up things" now that she's in high school. The thought of those things make her blush.
- Give Her a Normal Life: Michiru lamentably hoped that Hotaru would have grown up as an ordinary kid.
- It's Personal: Nehelenia appears in the end to gloat that she intends to take everything precious from the Moon Princess to make her suffer.
- Negated Moment of Awesome: Tuxedo Mask makes what turns out to be his final appearance in the anime… and collapses as soon as his leitmotif starts playing.
- New Powers as the Plot Demands: While alone in her room, Hotaru manages to create an energy-fueled simulation of the Big Bang followed by the development of the Solar System.
- Next Tier Power-Up: By the power of the rest of the Sailor Guardians, Sailor Moon unlocks the final level of her transformation. And her Kaleidomoon Scope turns into the Eternal Tiare.
- Platonic Co-Parenting: Hotaru is officially adopted by the Outer trio with Michiru and Setsuna serving as her "mommies" and Haruka as her "daddy". Haruka and Michiru are in a romantic relationship while their relationship with Setsuna is platonic.
- Plot-Relevant Age-Up: Hotaru continues to grow ever since Nehelenia's return. She reaches her official age after recovering her memories from her past life.
- Rule of Symbolism: Relating to the Foreshadowing example above, there are two objects on Mamoru's desk: a healthy plant and a lamp that's turned off. The way Mamoru is positioned makes it look like he's closer to the lamp with no light.
- Self-Deprecation: Minako and Makoto vouch that Usagi should be lucky to have relationship troubles when they themselves don't even have boyfriends.
- Shout-Out: Haruka compares Hotaru's Solar System projection to Fessenden's World.
- Skewed Priorities: Ami is concerned that Rei and Makoto are more interested in a language program's handsome host instead of learning the new language.
- Stalker without a Crush: Through regular mirrors, Nehelenia is able to spy on Usagi and Mamoru.
- Sudden Downer Ending: The battle results in the Sailor Guardians reuniting with each other along with Moon upgrading to her Eternal form. But after Mamoru returns to his apartment, Nehelenia appears in front of his mirror to gloat on how she'll take everything from the Moon Princess. Starting with her boyfriend, Mamoru.
- Tongue Twister: Usagi says a couple of them when she notices how monotone and spaced out Mamoru is on their date.
- What Happened to the Mouse?: One assumes Dr. Tomoe has no issues with three teenage girls raising his daughter instead of him.
