One day, Reiko, who lives with her daughter's couple, witnesses her son-in-law, Hikaru, frustrated and immersed in masturbation. Reiko couldn't take her eyes off that big, thick cock… When he learned that the cause was girls and lack of sex, he continued to seduce by playing with his cock no matter where he was. Faced with such an invitation from her mother-in-law, Hikaru, who accumulates sperm every day, could not resist… and give up. Since then, the two have secretly devoured their family's fun, but…