As Shunji embarked on his new life at a boarding school, he looked forward to a fulfilling student experience that would soon come to an end. Graduation day arrived, and as he walked home with his classmates, his heart swelled with hope for the future. Unexpectedly, it was none other than his stepmother, Miki, who approached him with a warm smile. Reuniting with the woman he had long admired, they celebrated their graduation together... until night fell and they found themselves alone, sharing intimate conversations throughout the night. Finally, Miki leaned in gently and whispered, "A gift for my grown-up Shunji," before planting a tender kiss upon his lips. And so, another step towards adulthood awaited him.

寮制の学校に進学した慎司だが、実りある学生生活もいよいよ卒業間近、新たな旅立ちへ希望に胸を膨らませていた。そして卒業式も終わり、学友との帰り道…笑顔で彼に駆け寄ってきたのは、義母・美希であった。憧れの女性との再会に喜ぶ慎司は、2人きりで卒業祝いを…。そして夜通し二人で語り合っていると「大人になった慎司君へプレゼント」と美希は優しく口づけを…。そして彼はまた一つ大人の階段を上るのであった。