Only because of the strange, control-reducing circumstances. If the MC wasn't being compelled to do it because of magic, it never would've happened.
I would not have called it magic per se.
Not sure what I would have called it, though.
I'd agree to an extend.
But Mana flirted relentlessly with MC almost from the start, so before long it actually was bound to happen.
If not in that case there little kitty cat would have kidnapped MC and invited his dick for a ... riding session in the gym backroom.
Regardless of age, race or profession every single woman MC meets wants to fuck him.
Most of them the fun way ...
The vampire girlies are aware of the risks they hear in their education, but as soon as it is confirmed MC is not turning into a ghoul and the truth about vampires having sex with humans do not go vegetable mode MC will be swarmed by one or three whole vampire clans ...