Shōtarō Torii attends the same high school as his best friend, Yūya Kanzaki. He openly envies Yūya's living situation with his stepsister, Mitsuki Kanzaki, frequently fantasizing about a potential incestuous relationship between them. This contrasts sharply with his own contentious relationship with his younger sister, Moa Torii; they constantly argue and fail to get along, with Moa often insulting him as "Bald" or "Baldy."

Despite his difficulties with Moa, Shōtarō readily flirts with various female characters. He makes advances toward girls of different ages, including Mitsuki's aunt, Nanami Akesaka. His behavior and interactions with others fuel several comedic situations within the series.