Yui runs a massage parlor with her husband. Sex with her husband is bland. One day, during her massage, she is captivated by a customer's erect penis, and they end up having sex. Having gotten a taste for it, Yui starts providing lewd services to her customers when her husband isn't looking. The number of customers increases through word of mouth, and Yui, a lewd little devil, provides more and more erotic treatments.