Today, Yumi works with her husband at a small local factory that has been supported by the couple and a few employees. Recently, their son Satoru has been helping out at the factory, and to those around them, they seem like a very close family. However, Yumi and Satoru have been in a forbidden relationship, hiding their love from their father. The two become obsessed with the "pleasure of immorality" that must not be discovered by anyone, and their obscene acts escalate in pursuit of thrills and pleasure...