Akira grew up as an only son in an ordinary family. His father, Hiroshi, and mother, Natsuko, were still close even though Akira had grown up, and they lived a very peaceful life. But one day, while studying late into the night, Akira suddenly remembered that he had to take care of something, and when he went to his parents' bedroom, he found Hiroshi and Natsuko naked and lying on top of each other... Akira was flustered by the unexpected sight. The two of them were even more flustered. Having witnessed the two people who were nothing more than his father and mother having sex, Akira has been worried about their behavior ever since...