I have several proofs mystery is indeed a vampire.
- His skin has no tan.
- He likes to wear hats/glasses for protection against the sun.
- He does night game, as day game can harm him.
- He is a master of seduction, as any vampire (Hollywood proved this).
- He switches young women regularly as the he uses their energy.
- He dresses outlandishly, as vampires do.
Now he obviously does not drink blood on their necks as this would be clearly visible. I think he and other vampires nowadays use technology to hide their actions better (like a needle or getting the blood of her finger).
I mean it's obvious.