Yuki has been living in a dormitory at a school far away for three years after leaving his parents' house. And on graduation day, which marked the end of his school life, his stepmother, Marina, came to meet him with a radiant smile. That night, Marina, who drank too much because of the joy of the graduation ceremony with just the two of them, got drunk. And she gently brought Yuki's hand to her chest as a graduation gift for her little boy. With her stepmother's permission, Yuki is free to do what she has long wished for. What a psychological and dangerous stepmother.