The wife is having an affair with the gym coach

I and Haruka have been married for three years. Lately, the clothes she used to fit into no longer do, and she wants us to go to the gym together to regain her old figure. I really don't like working out at all. At first I indulged her and worked out for a week, but I couldn't continue and gave up. Now she's the only one working out with the tall, muscular and charismatic coach.

I feel the distance between us growing, and thoughts of him sleeping with my wife keep coming to my mind. I decided to buy a voice recorder and put it in my wife's purse. In the evening, when she came home and went to the bathroom, I took out the voice recorder to check. And then I discovered the truth...