After his father's remarriage, the new stepmother, Miku, is closer in age to Kazuhiko than to his father, making their family dynamic feel unusual at first. However, Kazuhiko is gradually drawn to Miku's elegant and mysterious charm, slowly closing the emotional gap between them. In their everyday interactions as stepson and stepmother, Kazuhiko unconsciously finds himself attracted to her, unable to look away whenever she's near. One day, he accidentally discovers the intimate relationship between his father and Miku, leaving him shocked and emotionally conflicted. For the virgin Kazuhiko, the scene is an overwhelmingly arousing experience unlike anything he's ever known. From that moment on, something inside him changes. His feelings for Miku grow stronger and increasingly uncontrollable. Eventually, a forbidden relationship begins to blossom between them, giving rise to a new and illicit love story.