Hopefully at some point we get to see what would happen to all of the girlfriends if Rentarou never have met them. Because without him, they'd fall into despair. But that probably won't happen as that would pretty dark and would be serious. So hopefully we get to see at least one of their...
@bigboidan Good theory, but I do not think that is the case. The researchers can still take his family as a hostage without having Makoto being around. Other than that, there is no reason for him to avoid them other than attachment.
My guess is that, the stone guy is the Monarch as he has some purple on his four head. And he transferred his leveling ability he created to Sung Jin-Woo.