A man with abnormally large amounts of semen who can't get his erection to go down.
Upon investigation, it turned out to be a rare constitution found in one in tens of thousands, and he was asked to be a test subject for research.
The female doctor is amazed by his abnormal recovery power no matter how many times he ejaculates.
One day, during work, he accidentally got semen on the female doctor's face, and the affected area became smooth and supple.
They discovered it contained an exceptionally effective beauty component.
From that day on, including personal desire in the semen collection and facial cumshots, the female doctor keeps milking him...