Chiyo Mihama is a child prodigy who has skipped several grades to end up in high school. On her first day, she discovers that her class is full of eccentric individuals. Sakaki, who towers over Chiyo, is aloof and intimidating; Tomo Takino is loud and annoying; Ayumu "Osaka" Kasuga is absentminded but great at solving riddles; Koyomi "Yomi" Mizuhara is obsessed with diets and loves karaoke despite her awful singing; and Kagura, who is a competitive tomboy.

As the classmates become good friends over time, they experience their everyday lives together—things like school, studying, going on summer trips, and engaging in all kinds of shenanigans!