Outside that apartment, he was in control. Smooth, debonair, and aloof, Roy Mustang was the ultimate example of control, always completely cool, calm and collected, as the saying goes. Outside of his apartment, Roy managed to make people believe that's how he was all the time.

Inside that apartment, Roy was lost in his inability to keep that cool, calm, and collect attitude, his control stripped from him as his body surrounded the throbbing cock of another. He was lost in his inability to stay aloof when his own cock ached for the touch of the other's hand, his control vanishing as he cries out in pure, unadulterated ecstasy, convulsing as the sensation of finally finding release burns through his body.

The only one who could ever make him feel like that was the only one who would ever see his lack of control, but inside that apartment, there wasn't even a power struggle; Roy just gave it up willingly.