Kaoru and Akira lived together. Akira had always been deeply attached to his mother, and after their father's death, this tendency grew even stronger. Kaoru gently embraced him, and although they had never engaged in physical intimacy, she allowed him to touch her breasts and exchanged kisses with him, nurturing an unusual affection. As time passed, Akira became a university student. One day, when he suddenly announced, "I've got a girlfriend," Kaoru was overwhelmed by intense jealousy and finally gave in to the emotions she had suppressed for so long. Realizing she could no longer deny her feelings, she resolved to win Akira's heart back. Driven by this desire, Kaoru invited Akira on a one-night, two-day hot spring trip.