Ichika has long been in love with her older brother. She often acts intimately with her onii-chan, making him unable to resist dreaming of being able to touch those beautiful buttocks. One day, Ichika is confessed to by a tall, handsome, kind boy in her class. But because she loves her onii-chan, she cannot accept his confession. To avoid feeling embarrassed every time they meet, she doesn't know how to respond to him. He doesn't give up and wants Ichika to give him an answer. Ichika decides to tell him that she loves her onii-chan to make him give up hope. Knowing Ichika's weakness, he wants her to satisfy him. Ichika's onii-chan witnesses this and when he returns home, seeing those beautiful buttocks again, he cannot resist doing something unforgivable...