Kiyoshi Shusse is a core member of the eccentric Kimengumi group, known throughout the halls of his high school for his contradictory nature as both a strategic thinker and a notorious lecher. His family runs a bathhouse, an environment that directly fuels his reputation; his habit of trying to peek into the women's section has cemented his status as the school’s premier pervert. Despite these tendencies, a key aspect of his character is that he possesses a fundamentally pure heart beneath his lecherous exterior.

Within the Kimengumi, Kiyoshi stands out as the most rational and intelligent member, often acting as the brains of the operation. This makes him the "only sane man" when compared to his more outlandish friends, though his own considerable flaws prevent him from being a true voice of reason. His perpetual toothy grin has earned him the nickname Mukiba no Kiyoshi, or "Exposed Teeth Kiyoshi". Academically, he shares the group's struggles, having failed the high school entrance examination three times before finally gaining admission.

His family life adds another layer to his character. His younger sister, Kiyoi, initially idolizes him as a "cool big brother," but when his lecherous behavior becomes known among her peers, leading to teasing, his role shifts to that of a disappointing older sibling. This highlights the stark contrast between his familial persona and his school reputation. His closest bond within the group is with his best friend, Jin Daima. His frequent and often blatant attempts to seduce women typically end in rejection, solidifying his roles as a Casanova wannabe and a lovable sex maniac, a trait reflected in his room decorated with posters of half-naked women. Throughout the series, his core traits remain consistent; he leverages his slight comparative rationality while grappling with his comedic flaws.