Okamoto and Koizumi are the main characters of the story. Okamoto is a basketball player in high school, and he only enrolled to stay close to his girlfriend Tsugumi, with whom he has a complicated past. While they maintain a sexual relationship, Tsugumi holds Okamoto responsible for a scar on her back he caused as children when he accidentally spilled boiling water on her.
However, the introduction of Koizumi into the basketball club changes everything. Koizumi is small and slender, giving off a feminine appearance. In fact, Koizumi even secretly desires to be a woman. So much so, that you may have trouble discerning their gender when they dress casually.
