@BloodySorcerer -- Ah, thx. In that case, yeah, I'd just kill him and incinerate his body. Done and guaranteed.
I pondered the idea that the time traveler is his descendant, but the issue of paradox rears its head again. If he comes from this future that means he's a descendent of our MC with another woman. Exactly what he's trying to prevent. He'd be erasing himself. So, if he stops this from happening, he ceases to ever have existed. If he never exists, he can never stop it. Circular paradox. An almost identical paradox exists even if he isn't the decedent, but whatever.
Yeah, thinking too hard about it anyway. Real reason is that it is a roughed out plot device to serve as a framework for the ecchi.