Tatsuo Seino is a college student living alone in Tokyo. His family home is under renovation, so his cousin Masaru Fubuki and his aunt Harumi Fubuki are temporarily staying there. Tatsuo plans to return home as usual, but finds himself intensely sexually aroused by his mother, Fumie Seino. Unable to control his desires, he repeatedly engages in sexual acts with her, eventually climaxing inside her. Meanwhile, Masaru begins to see his mother Harumi as a woman, struggling with inner conflict over these forbidden feelings. As complex emotions and familial bonds intertwine, a story of incestuous desire unfolds.