Haruhiko Shimotsuki is a male art teacher who begins part-time at a school. He previously dated a woman named Mariko. Upon starting his teaching position, he meets Chitose, Mariko's younger sister, who confesses her longstanding love for him. Despite the significant risks of a teacher-student relationship, he enters into a romantic and sexual relationship with Chitose.

In general interactions, he appears affable and empathetic. However, his intimate behavior reveals a contrasting dominant side. He enjoys placing Chitose in humiliating situations and later refers to her as his slave. Chitose insists she belongs exclusively to him and accepts his treatment. Though he reciprocates her declarations of exclusivity, he soon becomes involved with another teacher, Tagami-sensei, who expresses willingness for a similar dynamic. Haruhiko manipulates Chitose into agreeing to this arrangement, resulting in a three-way relationship between himself, Chitose, and Tagami-sensei.

He has black hair and blue eyes.