Spoilers after the cut.
There are three subplots that comprise this chapter: Aizen getting philosophical, Ichigo plotting revenge, and a long-awaited return.
After the attempted attack on Reioukyuu (and taking out one of the Stern Ritter), Aizen has been incapacitated. Naturally, he blames Ichigo for this, even though Seireitei is the one leading him around like a dog on the leash.
Ichigo gets another rude awakening; this time it's courtesy of Yoruichi kicking him in what is likely a sensitive area. What ensues is some Beelzebub-esque comedy relief (oh, Kon, how I hate seeing you in Bleach after the first arc) and then some "real talk" about how to get back up to the Soul King's domain where Bach, Ishida, and the rest are currently.
And that's where things get weird.
Yoruichi obviously has an idea of how to get back to Bach's current location, but it involves someone who hasn't been seen in years, literally.
That someone is Grimmjow. The Sexta Espada has been down and out since getting trounced by Ichigo and Nnoitra in quick succession. His last appearance was earlier in the "final" arc when he threatened Urahara (we all assume that was him) and later on tried to barge in on communication between Ichigo and the former 12th division captain.
So yes, it's surprising to see Grimmjow return. Surprising, but not unexpected. After all, as we've seen with the "zombie" Arrancar and Aizen himself, this is Kubo's move!
As stupid as it sounds, I still expect Ulquiorra to show up again at some point. Not because it makes sense story-wise, but just because it's Kubo's move.
Although, now that Grimmjow is back, I don't necessarily expect he and Ichigo to just waltz back up to the floating tomb. Nah, there'll be bumps in the road galore, I'm sure.
Those two can't just get along.
