Her brother, who has loved Mayu since childhood, returns to his hometown for the first time in several years. However, he makes a shocking confession: he has come to tell their father that he is getting married. If it means she can stay connected to her brother, who is drifting away from Kokoro, she will give him everything that is precious to her. The sexual act between Mayu and her brother is immoral and sweet, but ends with a sad conclusion. ... Farewell, my only brother.