Married woman private lessons

The Kazama couple have been married for three years. When they first got married, they were passionately in love, but recently their sex life has fallen into a rut. In order to improve this, the husband prepares a vibrator, but his wife Yumi harshly scolds him for relying on the tool and puts it away in the cupboard. One day, Yumi, a returnee who is fluent in English, is asked by her nephew Toshio to teach him English conversation. A few days later, Toshio comes to her house and she immediately starts studying English conversation, but by chance Toshio finds the vibrator she had put away in the cupboard...