Ippei, a middle-aged man with no job and no hope, leads a miserable life. However, he lives off his brother Kenichi's generosity, enjoying a comfortable life while building an intimate relationship with Kenichi's daughter—his niece, Wakaba—and indulging in lewd acts every day, finding happiness in it. The catalyst was when Wakaba confided in Ippei that she couldn't have sex with her boyfriend. Ippei became aroused by Wakaba's voluptuous body and said, 'Let me teach you about men,' as he committed the act of indecency. Since then, they have been engrossed in forbidden acts without realizing it…
