Yuu been living in a dormitory at a school far away from home for three years. On the day of his graduation ceremony, which marks the end of his school life, his stepmother Marina runs up to him with a beaming smile... That night, Marina drinks too much and passes out in excitement at the graduation celebration just the two of them. As he walks her to her accommodation, she gently guides his hand to her chest as a graduation gift... Guided by his beloved stepmother, Yuu takes another step towards adulthood.