Takane is an 11-year-old boy whose mother promises him a new bicycle if he ranks within the top 100 on his school exams. Desperate for the bike because his old one is outdated and outraced by his friends', he tears his answer sheets upon learning he placed 112th. He lies to his mother, claiming 92nd place.

His family includes his younger sister, Tamaki, and their dog, Chris. The old bicycle is meant for Tamaki once Takane gets his new one. After accidentally breaking it on his way home from cram school, Tamaki's anger and her accusation about his lie fuel Takane's resentment, making him view her as a nuisance.

Searching for his missing dog Chris at a shrine one night, Takane encounters a supernatural figure named Yoyogi holding the falsified answer sheet marked "92nd." Yoyogi demands something Takane "does not need" in exchange for the paper. In frustration, Takane offers his sister, Tamaki. Yoyogi immediately transforms her into a shining object and swallows her. Horrified, Takane pleads for her return. Yoyogi agrees, but only if Takane wins a bicycle race against him using his broken bicycle.

This supernatural encounter forces Takane to confront his actions. Initially self-centered and fixated on the bicycle, he is compelled to reevaluate his priorities. The race becomes both a physical challenge and an emotional journey toward redemption, shifting his focus from winning the bike to rescuing his sister.