" There are multiple ways to become tier 4 , but all methods have a varying effect on future foundation .
The easiest method is by eating the breakthrough fruit , it creates pseudo tier 4 realm users , i myself am someone who used this fruit to breakthrough . But while it increases strength and allows one to level up beyond level 240 , the effects are not quite the same as a naturally ascended , hence this method is for the weak who cannot do it otherwise.
The fruit ofcourse is a very rare commodity not openly available in the market , however if you want it , emperor Cervantez does have it and he won't deny you to have it , but i don't think you will take the cowards way out so i will tell you the man's way to do it.