In the fifth installment of the popular series, Touka Rinne joins the cast! Every night, the intense sounds of moaning and the passionate, animalistic copulation reach Touka's ears, causing her to ache with longing. Her father-in-law, despite his age, possesses a powerful libido and makes love to his wife every night without fail. Known as the "eternally active viper," his vitality starkly contrasts with her husband's dull sexual nature. Gradually, the unfulfilled wife finds her heart shifting towards her father-in-law. Desiring to be embraced as fiercely as her mother-in-law, she can no longer suppress her lust and approaches her father-in-law for intimacy during her most fertile days.