The siblings Rizuki Mayama and Kyoya fight each other every time they meet. They don't get along so well that they start fighting even in the presence of each other's friends. One day, Rizuki comes home in a hurry in the rain and bumps into Kyoya at the entrance. Ritsuki gets angry, but freezes when she sees Kyoya's shirtless and wet body. His body was muscular, which Rizuki liked. When Rizuki noticed that she was staring at Kyoya, she tried to quickly leave, but she bumped into Kyoya and sprained her leg. Kyoya enters Ritsuki's room with a compress and a bandage, and becomes conscious of the fact that he is of the opposite sex as he enters his sister's room for the first time in several years. Kyoya tries to shake off his thoughts and leave the room before things get complicated, but Ritsuki demands that he give him a massage. Kyoya reluctantly decides to comply with his request out of guilt for causing him injury, but he notices this while massaging him. That his sister's body is what he likes.