Mana looks like a boy, but she is a pretty and cute girl. She has only had one experience with a man, so she consults her childhood friend Kenji, who acts as her older brother, about love and sex with her boyfriend. Kenji gives her serious advice, but he gets too enthusiastic and they end up practicing. The two of them try hard, but gradually they start to feel strange, and things escalate. The two young people let their instincts win over their reason.