Daisuke Ichijou possesses light brown eyes and brown hair, featuring a tanned complexion and slim, medium build. His relaxed lifestyle is reflected in casual attire choices like blue trunks, green shorts with a blue t-shirt, or brown shorts with a green tank top. Originating from the *Boin Lecture* and *Resort Boin* visual novels adapted into OVAs, he teaches at the all-female Koromo Gakuen. There, he conducts vocational counseling sessions using role-playing activities that occasionally incorporate suggestive scenarios, motivated by personal interests. During summer vacation, he takes a part-time job at Amanato Island's "Triton" beach resort after losing his money.

His personality merges a laid-back demeanor with an openly acknowledged fixation on large breasts, which frequently leads to sexually charged encounters with multiple women. Though generally easygoing, he exhibits a temperamental streak, becoming easily agitated by others. In intimate situations, he displays dominance, exemplified by reversing a BDSM scenario initiated by another character. His emotional responses vary across adaptations: he sometimes develops genuine feelings for characters like Nao Ihara or cousin Maya Koromogae, while other narratives show him indecisive, prioritizing physical attraction over commitment. This inconsistency extends to relational developments, with certain OVAs depicting romantic or sexual interactions with Maya while others omit them entirely.

He visits his unnamed grandmother's beach resort, reuniting with former students Nao Ihara and Mitsugu Tsukushino, reconnecting with cousin Maya after prolonged separation, and meeting new acquaintances Momona Amamiya, Kanae Shinjou, and Mika. These interactions spark complex entanglements where female characters pursue him, often overwhelming him yet drawing his participation. His familial ties include Maya as a cousin, though adaptations fluctuate in portraying their relationship, sometimes implying romantic or sexual undertones. Nao Ihara, another cousin, holds longstanding romantic feelings rooted in childhood when he cared for her during frequent hospitalizations.

Character development lacks consistency across media. In *Resort Boin*, his vacation becomes a series of erotic experiences with six women, though relationship progression shows no narrative continuity between OVA episodes—his dynamic with Maya shifts inexplicably between installments. His core traits, including perverse inclinations and professional conduct, undergo no significant evolution beyond situational reactions to female advances. Background elements remain minimally explored, with fleeting references to his grandmother and parents, who managed the hospital treating Nao.