Basically the uke has gained weight and wants to loose weight, on his way home he gets dragged into the gym, since they think he has booked a time with a personal trainer. Turns out that the uke has a condition that makes him get a hard on when he exercises, the personal trainer doesn't give a shit and helps him workout while helping him to jerk off at the same time. The uke finally falls in love with the personal trainer and confesses to the seme. The seme rejects him and stops working at the gym. Some time later the uke accidentally sees the seme on the street and chases after him, the seme takes him home and turns out that the seme has made a gym at home and offers to be the ukes personal trainer, turns out that the seme has a fetish to make a person achieve the perfect body, and kind pressures himself and others, namely his partners. They start dating each other, very wholesome story tbh.
Yaseru tame niha Ikanakya Dame desuka!? Hatsujou Taikan Training