You probably can't be friends with him anymore. You can be social and "know" him, but the differences between the ultra-rich and the masses impact every aspect of life and preclude a deep social connection.
The good news is that $100M+ is such a ridiculously large number that humans can't really do a good job of imagining what that means, so the psychological impact is less than if you found out your friend was worth $5M.
The good news is that $100M+ is such a ridiculously large number that humans can't really do a good job of imagining what that means, so the psychological impact is less than if you found out your friend was worth $5M.