As his graduation day approached, Atsushi was looking forward to leaving behind his fulfilling student life at the boarding school he had attended for three years. However, on his way home after the ceremony, he was surprised to see his step-mother Shiori running towards him with a smile on her face. Reunited with the woman he had always admired, they celebrated their graduation together. As Shiori became increasingly tipsy, she leaned in close and tenderly kissed Atsushi before whispering, "This is my graduation gift to you...". With that, Atsushi took another step closer to adulthood.

寮制の学校に入学して3年、間もなく卒業を迎えるあつし。充実した学生生活も終わりを迎え、卒業式当日…。誰も来ないはずの帰り道、向こうから笑顔で駆けてくる女性は、なんと義母の翔子であった。憧れの女性との再会に喜ぶあつし。2人きりの卒業祝いでほろ酔いの翔子は「卒業祝い、あげるね…」と優しくほほを包み込み、そっと彼に口づけを…。そして彼はまた一つ大人の階段を上っていくのだった―。