After his father's remarriage, Yuu left his family home to attend school, enjoying a fulfilling campus life and now finally reaching graduation day. On his way home, he is greeted by his smiling stepmother, Ikumi Shiramine. Though he had long suppressed his feelings for her while living alone, this unexpected reunion reawakens emotions he once kept hidden. That night, celebrating his graduation together alone, their conversation flows endlessly, filled with warmth and joy. Then, Ikumi whispers, "A gift for the now-adult you," and presses her lips against his—crossing the line, their relationship takes a bold, intimate turn.