In lieu of a full translation, allow me to offer a synopsis:
Kyoko is having sex with her husband Yusaku a little more enthusiastically than usual. "It's always better with someone you love," she says, but she is still not satisfied, and finds herself masturbating even after a prolonged session.
She later meets her tormentor Gokaichi at a tennis court, but he has ordered her not to wear the typical "underskirt" worn by female tennis players, she only has regular panties underneath. She is shocked when she learns she is expected to play "as is". He offers her a match: best three out of five games, and offers a wager: if she wins a game, a day comes off her "contract", if she wins the match, she can have him do anything she wants, even end the contract.
But every game she loses, she must take off one piece of underwear, and if she loses the match, she must do something for him. She's concerned about doing this in such a public place, but he assures her that they are too far away from everyone to be noticed, and the older couple on the next court can't see very well anyway. Kyoko agrees, thinking that her experience and Mitaka's training will give her an edge, but it turns out her tormentor is an excellent player, even having participated in major tournaments. After losing the first game, she removes her bra, then after losing the second, her panties come off. He records her showing him by lifting her skirt.
She is embarrassed having nothing on underneath her short skirt, which reveals a lot to the others on the court. It also takes her off her game, and she is easily defeated. However, her "punishment" is simply making him cum, in a secluded alley near the court. Humiliated, she comes to realize that "I'm not...the person I used to be...The identity I've built has been destroyed by this man...all that's left is this lecherous woman who gives herself up to pleasure".
Gokaichi brags that he "knows her better than her husband" and that she is his "body and soul".
But he wants some insurance after all...
According to the postscript, Hoshino will do one more story to end this series...we shall see...