My wife, Mari, became involved in a jiujitsu gym after my careless remark about her weight. As she started going regularly, I noticed that not only was her body getting toned, but she also began wearing flashy underwear and always had her phone with her. Something felt off about her behavior. Despite my suspicions, I couldn't muster the courage to confront her. To make matters worse, she seemed to be crossing lines repeatedly with our handsome trainer...

僕の「太った？」という不用意な発言が原因でとある格闘技ジムに通う事になった妻・茉莉奈。入会してからというもの、みるみるうちに身体が引き締まる茉莉奈を見て僕は安心、油断しきっていた。しかし、その頃から体型の変化だけではなく妙に派手な下着、必ず出ていた電話に出ないなど茉莉奈の異変にも気づく様になっていた。問い詰める勇気がない僕を嘲笑うかの様に、妻はイケメントレーナーと何度も一線を越えていて…。