Yumi Kazama, my 42-year-old stepmother, lost her husband at a young age and has been living alone ever since. Despite her voluptuous and alluring figure, she dedicates herself wholeheartedly every day to taking care of our married life. One day, I accidentally discover her masturbating to ease her loneliness. In that moment, I see her true self, and a secret affair begins between us, hidden from my wife.