The protagonist's father is transferred overseas, so he temporarily stays at his father's colleague's house. Initially, he thinks, "I'd rather live alone, why do I have to live with others?" and is dissatisfied, but he notices the colleague's wife Yuri's sexy charm, and his masturbation frequency skyrockets. However, one day, he witnesses Yuri having a forbidden relationship with an older man from the same apartment building. While masturbating excitedly at the sight of Yuri being fucked by the old man while blindfolded, the old man waves him over. "Eh, c-can I put it in Yuri?" he hesitates, thinking, "But, isn't this bad...?" However, he reconsiders, "No no, this chance might never come again in my life," and finally decides to make a move on Yuri.