Yuu attends a boarding school. His fun school life comes to an end in the blink of an eye, and on the way home after his graduation ceremony, he sees a woman running up to him with a smile on her face... The smiling woman is his stepmother, Sei, whom he secretly has a crush on. Yuu is Kokoro to be alone with the man he loves. That night, he takes her back to the inn, where she is drowning in alcohol... Sei accepts his feelings and kisses him tenderly, saying, "This is a present from me." And so, Yuu begins to take his first steps towards adulthood.