Haru Kasugai attends Eidai High School and plays in its koto club. Official data confirms him as the tallest character in the series. Within Eidai's koto club, he joins Sentaro Miya—a notably shorter member—and the equally tall Akari Kobayakawa to form a trio. Their distinct "tall-short-tall" physical contrast defines the group during Nationals competitions. Eidai's koto club faces Tokise High School as rivals in these national events.