Kazui is the 2nd Yhwach.
Think about it, the shit ton of symbolism of Ichigo representing the soul king in the anime. And Kazui is the son of Ichigo aka mini soul king. Kazui is fucking with hell and he'll (no pun intended) be the viillain in the hell arc.
>b-ut
Nope
>That's impossib-
Shut the fuck up, he'll be the villain because I said so

symbolism