Riko is a housewife living with her husband, daughter, and son-in-law. She had been leading a comfortable life without any troubles, but since her husband started remote work, petty arguments between them began to increase. One day, Riko witnesses her son-in-law Masaki's impressive manhood in the bathroom. The stimulating sight she hadn't seen in a while unintentionally stirs her instincts… and Masaki starts persistently approaching Riko as if he had planned it! "Mother-in-law, you must be frustrated… Let's become animals together!" Riko's abundant, overflowing breasts are squeezed by Masaki, and she is dragged into the whirlpool of an affair…
