Per wiki policy, this page is Spoilers Off. You Have Been Warned.
Is Yuu an Alien?
A central Driving Question of the story is whether Yuu is truly an alien, or just a chuunibyou. Here's a rundown of the evidence for and against: The Evidence
The Story's Themes
- AGAINST: Umika, Haruno, and Matataki are united by the fact that they've had bad experiences which warped their present personalities. It'd be thematically consistent if Yuu was a human girl whose unconscious mind "ran away" from a trauma by fabricating a new personality, similar to Haruno's backstory but to a much greater degree. Furthermore, HoshiTele has strong K-PAX vibes, and this twist would be very similar to a twist found in that film.
Her Origins
- FOR: She has a mysterious origin, appearing in a lighthouse with no memories after a shooting star whizzes past.
- AGAINST: Her behavior has all the hallmarks of a dissociative fugue, a medical condition where somebody disappears from their old life unexpectedly and then turns up somewhere else with amnesia.
Self-Identity
- AGAINST: Her famous Heel Realization of "I'm a Bad Alien" suggests that she's not one. Using the word "alien" for an extra-terrestrial entity is very Earth-centric. While an alien using it when communicating with humans can be justified by the fact that it's a generally recognized term on Earth, it'd be absurd for an alien to think themselves as an alien, rather than whatever astronomical entity they come from.
Psychological Repression
- AGAINST: She's excellent at reading other people, but astoundingly bad at understanding her own negative emotions, even simple ones like jealousy. While this seems incongruous on a character level, it'd make more sense if her unconscious mind was intentionally repressing parts of her old personality that she doesn't like.
Teleportation
- FOR: She appears in Umika's room with it being proven later that it was not a dream. Unless she broke into the house, there is no way for Yuu to have entered the room if not for being an alien.
- AGAINST: This would also be explained by her entering a fugue state and breaking into the house while sleepwalking.
- Even though, keep in mind that her sister also lives with her. How would she not notice Yuu entering the house and heading to Umika's room? Especially if Umika never said anything about Yuu coming over to spend the night?
- When they all have breakfast together in chapter 34, Honami asks point-blank, "When did you even get here?" She doesn't seem particularly bothered by the fact that Yuu showed up out of nowhere, while their mom is squealing with excitement that Umika had her first sleepover.
- Even though, keep in mind that her sister also lives with her. How would she not notice Yuu entering the house and heading to Umika's room? Especially if Umika never said anything about Yuu coming over to spend the night?
Foreheadelepathy
- FOR: She seems to have some skill at reading minds through touching foreheads together, including painting a picture that sorta looks like Matataki if you squint hard enough.
- AGAINST: All her "mind-reading" can easily be done by a skilled Cold Reader. Even when she hasn't done "foreheadelepathy" with someone, she can effortlessly suss out when somebody's hiding something, as demonstrated by her conversation with Haruno in chapter 25.
Electrical Powers
- FOR: She claims her alien powers are providing electricity to the lighthouse, and when she "disappears" in chapter 23 it accordingly loses power.
- AGAINST: Matataki seems suspicious of how the lighthouse is generating power by itself in chapter 36, and in chapter 44 we see her leafing through Akikazu's journal and intently studying the schematics of the lighthouse found inside, implying there's more mysteries to be uncovered.
- FOR: In chapter 36, Matataki spitballs the idea Yuu has the power to cloud other peoples' minds, since it makes her head go fuzzy whenever she tries to get a handle on Yuu.
- AGAINST: No concrete proof for this hypothesis is given, so it may just be apophenia. Matataki generally has a headache every time she deals with Yuu, so that doesn't say much.
Cosmic Language
- FOR: She's fluent in the "cosmic language". Per chapter 43, its dictionary may have been published on Earth by Haruno's grandfather or some other related party to lay the groundwork for a cultural exchange.
- AGAINST: There's no proof it's anything more than a Conlang somebody invented and published on Amazon. Yuu may have just been a lonely girl who became friends with Haruno's grandfather over ham radio, and speaking the "cosmic language" was part of their game.
The "Alien Voice"
- FOR: The girls come into contact with a mysterious voice on a meteorite-powered radio who claims to be one of Yuu's comrades and who offers to tell her about her past.
- FOR: The voice claims it can read any thoughts directed at them, and Matataki's shocked expression suggests that is what she was thinking at that exact moment.
- AGAINST: The manga conspicuously avoids showing any hint of a UFO or anything otherworldly, teasing the audience with Maybe Magic, Maybe Mundane. Furthermore, manga and anime often treat chuunibyou like a disease. There are other examples of characters being "infected" and becoming devout zealots of a chuuni worldview. This voice may just be the Sanae Dekomori to Yuu's Mori Summer.
- AGAINST: The voice's ability to read minds would be more impressive if it hadn't said the most obvious thing in the world at that particular time. Matataki is shown concentrating hard, like she wants them to keep reading her thoughts to confirm it's true, but it's not shown whether the voice is correct or not. Also, since the girls are literally at the foot of the lighthouse, it would be trivial for somebody to climb to the top and watch their reactions as a form of Cold Reading.
The True Identity of the Alien Voice
The girls make contact with a self-proclaimed alien voice in chapter 39 who seems to know both Yuu and Haruno's grandfather, but its true identity is shrouded in mystery and uncertainty. It could be...- A genuine alien. Yuu was telling the truth about being an extraterrestrial the whole time.
- Kei Akizuki. She seems like the kind of girl who'd try and communicate with aliens over radio as a six year old. Her transmission was picked up by Haruno's grandfather, leading to an Intergenerational Friendship over ham radio. It may seem overly convenient that she becomes Yuu's Friendly Rival, but Is the Order a Rabbit? recently revealed that Cocoa Hotto starting a work-stay program at the house of her mother's deceased best friend was just a twist of fate, so a Contrived Coincidence like that isn't out of place in Kirara.
- The spacey middle schooler shown taking an interest in the RRA's booth at the cultural festival, who will presumably become their kouhai next year. She's a Sanae Dekomori-type who internalized Yuu's chuuni nonsense and she's going to Yuu's school to aid and abet her "master's" delusions.
Haruno's grandfather published the Cosmic Language dictionary
The manga has, as of chapter 40, given no indication how or why an ostensibly alien dictionary would be available for purchase on Amazon. Regardless of whether Akikazu really was in contact with aliens, or if it was just some elaborate conlang (based on Esperanto) he invented with some friends over ham radio, he's the only "Earthling" we've seen who's in a position to have it published. Yuu is a Body Snatcher
Much like the above stated, Yuu may not be an alien, but rather, the actual "alien" is sharing a body with her. Prior to Yuu being introduced, a bright light shot through the sky. The alien is actually a parasite that latched itself onto Yuu and gradually changed her biological makeup. It would explain her lack of memory of her life prior since she was now a hybrid.