MC is not that bad a guy. I mean he could try to steal the other guy's gift with drain, but he doesn't. If that works he could steal every other players skills as well. But he would already be ridiculously OP with just growth and drain.
If he only needs contact with the mucus membrane then he could just put a finger in good boys mouth til he gets the growth skill... Technically that should work and I don't see good boy saying no to doing that. Alternatively they could just kiss lol