A married woman personal trainer seduces me with her beautiful butt and a devilish smile, reverse NTR

My wife, who has been suffering from weight gain and is currently suffering from dieting, was watching a video and was stretching. The female trainer uploaded to the video sharing site is said to be Yu, and it appears that she is running a personal gym in Tokyo. A few days later, I decided to go to Yu's personal gym with my wife to try it out. He was very kind during his training, but only in my time we were strangely close. Then, in a low voice that my wife couldn't hear, she asked me to take one-on-one lessons...