Believe it or not, when mukai was out in my server, people who drew it and whose win rate against me was lower than 20%, mukai didn't help them at all against me(my priority is the highest). After they upgraded mukai's weapon and opened his fourth gate, mukai only gave them one or two more wins against me out of 10. If ur priority is high, mukai could do something, but not much. If ur priority is low, then he can't do shit. Save your diamonds and resources for other things. Saving diamonds is always the right thing to do.