User blog comment:Xilinoc/Ch. 683 - The Dark Side of Two World Ends/@comment-1970092-20160721122023

I should point out that this was Aizen this entire time, probably since last chapter actually. Notice that when Ichigo actually arrives, his Bankai is untouched and brand new. Aizen comments "I see... So you're seeing Ichigo Kurosaki. How Fascinating". To me, that shows that Ichigo wasn't there yet, and Aizen wasn't even intending on Ichigo showing up.

So pretty much, this was Aizen vs Yhwach since last chapter when the reunited~