Our MC is Miya’s regular customer, but he can’t muster up the courage to confess. Then one day he walks in on some other customer having sex with her and ends up masturbating like there’s no tomorrow.

Now, in your typical hentai, this would be a NTR situation. But not here. He didn’t actually enjoy seeing her having sex with someone else. It takes a professional like Miya to figure out what his real fetish is and how to get him to open up. And finally start having sex with her.
*All characters depicted in this work of fiction are adults, regardless of their visual representation or textual description, and are not based on any real person*