Upon learning that her sister and brother-in-law are longing for a child, Mako initially feels hesitant but gradually resolves to help fulfill her sister's dream. However, as pregnancy fails to occur, her relationship with her brother-in-law grows increasingly frequent and intense. Eventually, with her sister often present in the next room, the brother-in-law repeatedly demands creampie sex from Mako. Throughout this process, Mako is forced to confront her inner conflicts and emotions, ultimately questioning how she should choose to live her life.