Kosuke Atami begins as a high school student reuniting with his childhood friend, Shizuka Himenogi, after years apart. Their initial reunion reveals mutual dislike stemming from changed personalities, though they gradually accept their differences and rekindle their friendship. A childhood marriage promise, viewed by Kosuke as a game, is taken seriously by Shizuka, who retains romantic feelings for him. Despite this, Kosuke frequently pursues sexual relationships with other female classmates. These encounters are motivated by his lecherous tendencies, kind-hearted nature, and luck, as he attempts to solve their personal problems.

His character consistently uses sexuality as a tool for helping others, blending gag comedy with eroticism. This pattern continues into adulthood. By 2006, at age 34, Kosuke is a divorced host, maintaining his core traits of combining sexual interactions with problem-solving to aid women. This adult phase is depicted in the manga sequels *Angel: the women whom delivery host Kosuke Atami healed* and *Angel season 2*, serialized in *Weekly Manga Goraku*, showing him applying similar approaches to adult relationships.

Kosuke's background includes minimal familial details; his parents appear occasionally in ancillary media like specific OVA voice credits, but these do not contribute substantively to his character development or backstory. His core narrative remains focused on his relationships and his role as a helper, whether in high school or as an adult host.