Kiyoshi Shusse serves as a core member of the eccentric Kimengumi group. His family runs a bathhouse, an environment directly fueling his characterization; his habit of peeking on the women's side cements his reputation as the school lecher. Despite these perverted tendencies, he possesses a fundamentally pure heart.

Within the Kimengumi, Kiyoshi stands out as the most rational and intelligent member, often acting as the group's brains. This makes him "Only Sane by Comparison" against his more outlandish friends, though his own flaws prevent him from being a true voice of reason. His constant toothy smile earns him the "Perpetual Smiler" designation.

Family dynamics add complexity. His younger sister, Kiyoi, initially idolizes him as a "Cool Big Bro." However, when his lecherous behavior becomes known among her peers, leading to teasing, his role shifts to that of a "Disappointing Older Sibling," highlighting the contrast between his familial and school personas.

Academically, he shares the group's struggles, failing the high school entrance exam three times before finally gaining admission. His closest bond within the Kimengumi is with best friend Jin Daima. His frequent attempts to seduce women typically end in rejection, solidifying his roles as a "Casanova Wannabe" and "Lovable Sex Maniac," reflected in his room decorated with posters of half-naked women.

His core traits remain consistent throughout the series and subsequent media; he leverages his slight comparative rationality while grappling with his comedic flaws.