Osamu Tamura, or 'Parou', started cross-dressing in middle school because he wanted to attract Shibuya, a heterosexual boy.

Spoiler

After Osamu confesses to him, Shibuya agrees on going out with him but only when he's dressed as a girl. They start sleeping together and Osamu even keeps visiting him when Shibuya no longer goes to school after failing to get into a high-ranked high school. Although blaming it on him and treating him like dirt, Osamu stays attached.