Aight basically
When Yuta killed Kenjaku he had the curse Rika eat him to be able to take his ability
So after his fight with Sukuna, Yuta was on the verge of death after he got cut in half
As a result, he had the consiusness left to transfer his brain and put it in Gojo's head, thus copying Kenjaku's ability.
However he can only do it up to 5 minutes, and nobody knows what will happen when its up
