Sister-in-law close coaching

Taro has turned 30 and is concerned about the fat around his stomach, so at the suggestion of his brother, he gets his sister-in-law, Ayuka, to work with him as a personal trainer. And then the first day... Taro's crotch bulges out from his tight training clothes as he stretches his body overlapping Ayuka's. Ayuka doesn't even look at Taro's crotch... A few days later, the two are sweating and training hard again. His sister-in-law's coaching brings about changes in Taro's body, but...