The story of two sets of mothers and their sons. Tatsuo Kirishima, a son studying at a university in Tokyo and living alone, and his beautiful mother, Eikuko Kirishima, who eagerly awaits her beloved son's return home at their family apartment. Then there is Miho Sakaki, the mother next door, and her eldest son, Yohei Sakaki, and her second son, Yasuhiro Sakaki. One day, Tatsuo returns home as planned with his girlfriend, but he cannot contain his sexual excitement towards his mother, leaving his girlfriend aside and repeatedly engaging in sex after indulging in lewd fantasies. Around the same time, Yasuhiro catches his own mother, Miho, and Yohei having sex, becoming jealous of their enviable relationship to the point that he infiltrates the balcony of the neighboring room and witnesses the incestuous act between the Kirishima mother and son. As Tatsuo finishes and comes outside, Yasuhiro attempts to propose a lewd plan…
