Mio lies to save a friendship and ends up destroying the thing she was trying to protect. The movie knows that cowardice dressed as kindness is still cowardice. What hits is watching her realize, too late, that the person you love most deserves the truth more than they deserve your comfort.

Mio coasts through high school with her two closest people: Arata, her childhood friend, and Madoka, her best friend. Their days blur together in Ikebukuro's streets until Madoka confesses she's fallen for Arata. The revelation hits Mio hard because she realizes she harbors the same feelings. Paralyzed by the fear of shattering their friendship, Mio chooses avoidance, pushing Arata away with coldness and distance. The tension between them escalates into conflict. Eventually Mio accepts what she's been running from and decides to face Arata and make up with him. She heads out through the rain to find him, but a car accident stops her on the way. When she comes to, she is riding a train across water beside swimming whales, and it arrives in a version of Ikebukuro that feels subtly wrong. A self-proclaimed guide named GiMON and a mysterious girl named Kiku point her toward a way out, but leaving requires a precious memory she cannot recall.