“Thorough one-on-one coaching from a female trainer—now taking reservations!” Drawn in by the ad, my wife and I visit a private gym in Tokyo. Our trainer, Rio, is attentive and helpful, but her unusually intimate distance leaves me flustered. When my wife steps away to shower, Rio suggests a private lesson for just the two of us. A few days later, I convince myself that it is only a workout and return alone to the gym where Rio is waiting...