My friend's wife is a lewd tutor

Mio teaches studying to her husband's friend as a private tutor. Her recent problem is that her students are not concentrating on their studies. One day, one of his students, Nakano, witnesses an erection while studying. Mio realizes why her students haven't been concentrating on their studies, and decides to satisfy her friends' pent-up sexual desires, saying, ``If they'll focus on their studies...'' ...It turns out that she is actually a ``slutty tutor'' who loves sex.