Despite having a girlfriend, Seiji couldn't resist his stepsister Kanon's temptation, which only lasted for one month until the tournament. At first, he felt guilty but as Kanon's happy face showed every time they had sex, Seiji's heart slowly became numb. As the tournament approached, Kanon's desires gradually escalated and she eventually began to desire him even within the school. While they were having sex in the clubroom, Seiji heard her girldriend's voice approaching the clubroom and for the first time, he felt genuine fear. What was he doing? In the midst of this confusion, he missed a golden opportunity at the baseball club tournament and was defeated. Seeing Kanon supporting him with her unconditional love, Seiji finally decided to end his relationship with Kanon. However, a week later, the 'memories' left in Seiji's body were more deeply engraved than he had imagined...