Yui started dating Mitsuaki, whom she met at her part-time job. Mitsuaki invites Yui to his home to introduce her to his father as his first girlfriend. Kouzo, who has been living with Mitsuaki alone since his wife passed away, is unexpectedly captivated by Yui. One day, pretending to listen to Yui's concerns after a trivial quarrel with Mitsuaki, Kouzo pressures Yui. Behind the innocent love, Kouzo and Yui's immoral physical relationship deepens.
