Oshiohshi is the surface, where Manaka, Hikari, Chisaki and Kaname go to school, as well where Akari worked in the pre-timeskip.
Trivia[]
• It becomes the living place of Akari after the timeskip, where she goes to live with Itaru and Miuna.
• This is where Manaka, Hikari, Chisaki and Kaname go to school.
• The place was first doomed to get into an Ice Age, however, the process was halted in Episode 25-26.