Follows the "I wonder if it would feel good to have something up the ass?" bicurious yaoi trope. "Straight" dude decides he wants to experience a prostate orgasm and his centre of pleasure shifts from genital to anal. He coaxes a doctor at the hospital into giving him a good dicking down and becomes addicted.
They should've switched at least once imo.
Hot long-haired top, good smut, decent romance: 4/5.
Sensei Shokushin Shite Kudasai