Natsuki Ikaruga is invited by a mysterious woman, Catherine, to search for a treasure in his grandmother's house; he dives to the bottom of the ocean in a submarine and encounters a mysterious capsule with a girl sleeping inside.
Atri, who is supposed to be with Cathrine, comes back to Natsuki; she has a new master; she falls into the ocean while carrying her master and fails at cooking; Atri receives a very important order from Nonko and tries to remember what it is.
Natsuki accompanies Atri who is on her way to school; when they arrive, they find that most of the school is underwater; although they managed to get into the school building, inside it was full of empty classrooms and an unexpected teacher.
Natsuki sets his heart on creating a tidal power generator that utilises the ebb and flow of the ocean's tides; he dives back into the ocean to find some materials and salvages some resin from the ruins of Ryuuji's family's factory.
If Natsuki sells Atri, he can get batteries; he can no longer think of Atri as just an average humanoid.
Natsuki's life experiences a big shift after becoming a teacher and starting a salvaging service; rumours of a school lit with electricity attracts new students and activities around the school regain a sense of liveliness.
Kensho Ono
Natsuki Ikaruga
Hikaru Akao
Atri
Minami Takahashi
Minamo Kamishiro
Yoshimasa Hosoya
Ryuji Nojima
Yōko Hikasa
Catherine
