And this chapter pretty much cemented my interest in the new arc - and also foretells that no, Kubo hasn't forgotten all the threads he's been weaving this entire time. In fact, it may be now that they're finally starting to slowly come together.
First off, I think it's fairly evident by now that the hollow Isshin fights in these chapters - the "white" hollow Aizen named - is the one that is also now inside Ichigo in some form. For me any questions about that were answered last chapter, when the hollow opened its mouth wide and screamed in a style completely (and I imagine purposefully) mimicking the Shirosaki-Ulquiorra fight on the dome. If it's not the same hollow, Shirosaki has to be the hollow's twin. (And this is all the more interesting to me - when Ichigo first meets Shirosaki, Shirosaki's immediate response is that he "ain't got no name." Intriguing, considering that Aizen himself named this one.)
This leaves, of course, a lot of unanswered questions. How does Shirosaki end up in Ichigo to start? Masaki definitely has contact with the hollow here - it looks like he bites her when she catches him - so that's maybe a throwback to the Fullbringer arc, at least, and the notions that hollows can somehow infect or alter the offspring of those who've had contact with them.
Then again, this hollow is entirely different - and that difference is the second thing that intrigues me about the chapter. Aizen indicates the hollow has been created from a shinigami's pure soul (and I haven't looked at the raws, but I wonder if the "inner whiteness" talk has something to do with an innately good/pure/special shinigami). So I suspect the interactions of Masaki and Isshin with this hollow might have different ramifications here. This makes me glance back to the Espada differently as well - were they created in a a similar manner? This chapter indicates that all of this happens post-Urahara's-banishment: are the Espada evolved forms of this "shiro" hollow? And were they, too, created with the souls of shinigami? We know the hougyoku was used to create them, but not how. Kubo indicated that both Ulquiorra and Grimmjow were animal-like hollow in their early days - but he didn't indicate how they moved from those "evolved" hollow forms to very human ones. I suspect the hougyoku and perhaps the souls of shinigami contribute to that next step. I also imagine this also ties in with some ways with Ulquiorra's "heart" comments during his last appearance on the dome, and the Fullbringer arc's indication that hollow holes are where the hollow's heart used to be. This also makes sense of how shinigami-esque the Espada were, fundamentally - and I wonder if it won't have something to do with their redemption, and their contribution to this arc, in the end.
Now down to other business: Masaki is a badass, and Aizen is still a (wonderful) jackass. Is anyone else seeing Orihime all over Masaki? I don't know if it's just that Kubo's women have all started to have that sort of commonality, or if we're supposed to be deducing something from the similarity; fandom would shit if somehow Ichigo and Orihime ended up siblings. But I digress. Anyway, she takes care of that hollow posthaste - it's nice to see a badass woman take care of business like this, and it's easy to see how the mother might have influenced the son: she wants to protect people, too, no matter who they are.
As for Aizen...well. Puppetmaster, evil, etc. But I'm still curious about his motivations for all this. He's still a character who's very much in play - even influencing events from his prison in Seireitei - and I still think a lot of this is a part of his larger plan to...something. And the "something" is what I wonder about. As far back as the Soul Society arc, Aizen talks about an "emptiness" in heaven, and confronts Urahara about the Spirit King before he's sealed away. As much of a douchebag as he can be, I suspect that before too long we'll see how all this ties together and that perhaps - even if his actions were insanely misguided - the motivations behind them might not be.