Yuichis mother, Eriko Miura, is the one and only being born from her heart. Feeling it was her duty as a mother to ensure her son acquired proper sexual knowledge, she strongly embraced her responsibility. Driven by this conviction, she decided to become Yuichis first woman herself. However, due to overprotective upbringing, Yuichi became reclusive and withdrawn at home. Amid this situation, signs of change began to emerge in their relationship.