A story of two pairs of mother and child. Tatsuo Kirishima, a boy who goes to a university in Tokyo and lives alone. And Kirishima Towako, a beautiful mother who is looking forward to the return of her beloved son in her parents' apartment. And Miho Sakaki, the mother of the family living in the next room, Yohei Sakaki, the eldest son of her son, and Yasuhiro Sakaki, the second son. One day, Tatsuo went home with her as originally planned, but she could not forbid sexual excitement for her mother, and she was left behind and sexually acted many times after an obscene delusion. .. At the same time, Yasuhiro witnessed his mother Miho and Yo-Hey having sexual intercourse, and was jealous of the relationship that was too enviable. Witness. Then, Yasuhiro Sakaki tries to come up with an obscene plan, aiming at Tatsuo Kirishima who came out after one shot.