She lives with her husband and two sons... The two sons are still at an age where they can't stop being so dependent on breast milk, so they bury their faces in Seiko's buttocks and caress her body as much as they want. Seiko, the mother, reacts to her sons' caresses and learns the joy of sharing her body with them. The sons' caresses escalate, and they forcefully insert their erect cocks into Seiko's anal passages. Seiko is overcome with a pleasure different from that of a pussy, and her body squirms with pleasure as she engages in a threesome with her sons...