Yuya, a son, is Kokoro when his mother's friend, world-famous bodybuilder Keiko, whom he has always admired, comes to visit. Seeing her well-trained, magnificent body for the first time in a long time, Yuya is captivated by her beauty... That night, the two are happy to be reunited and renew their friendship. Keiko, who has been troubled by her relationship with her husband, is moved by Yuya's sincere feelings for her, and she ends up making love to him. The two sneak away from their mother's eyes and spend a brief rendezvous. Then, the night before Keiko is due to return home, Yuya visits her room...