Mamimi is a 17-year-old high school truant who dates Naota's older brother Tasuku but immediately starts flirting with Naota after Tasuku leaves Japan. She's basically always smoking, hanging around under bridges with a camera, living that chaotic life. Fans often note her habit of calling people and objects "Ta-kun"—supposedly after her nickname for Tasuku, though she uses it for Naota too, which he's definitely aware is kind of weird. She calls Tasuku "Tasuku-sempai" out of respect since he's older.
Her whole thing with fire is murky. The story suggests Tasuku saved her from an elementary school blaze, but it's hinted she might've actually started it herself. Either way, she's obsessed with fire and has this shaky grip on reality—she genuinely believes the robot Canti is a video game god called Cantido and burns stuff as sacrifices to him. Most people find her kind of vacant and annoying; her classmates especially treat her poorly.
But here's the thing: when nobody's watching, Mamimi gets genuinely destructive. She can't seem to control her own life or make real decisions, which probably explains the constant smoking and how she clings to people like Tasuku and Naota. She actually loves looking after anything that seems helpless—right up until the moment they show any independence, at which point she just. leaves them. This cycle defines her whole arc, and it all culminates badly when she adopts a robot terminal that ends up going haywire and destroying everything.
She's also pretty sexually frustrated as a teenager, constantly trying to get physically close to Naota in ways that make him deeply uncomfortable. When he asks why she won't leave him alone, she just says, "If I don't, I'll overflow."
Most people just call her Mamimi. Naota's friends joke that she's "Naota's Wife." Haruko shortens her last name to "Sameji," and Amarao just refers to her as "that high school girl."
Content compiled by AnimeList.moe from publicly available sources.
