Yuna comes to her husband's parents' house to visit her father-in-law, Toru, who was injured in an accident. Since losing his wife five years ago, Yuna has been feeling down, and wants to cheer him up. One day, while she is helping him take a bath, Toru pushes her down. He licks her lips, entangles his tongue, and then kisses her genitals passionately, making obscene sounds. Yuna is frightened and resists, but she experiences her first orgasm. Whenever Toru is not looking, he uses his lewd tongue to attack Yuna's sensitive body...