Sota, who married the daughter of the Ohara family as an adopted son, was spending his days captivated by the voluptuous huge breasts possessed by his mother-in-law, Rio. One day, Sota ended up helping Rio with her stretching. Sota, who reached the limit of his patience with the huge breasts swaying lewdly before his eyes, attacks Rio. And Sota, who also saw through Rio's timid personality, further seeks out Rio. Their actions escalate, such as playing with Rio's naked body covered in bubbles in the bathroom, or indulging in lovemaking in secret during family gatherings...