Never one of my favorites, Aizen (or Hinamori for that matter), but I've recently taken a rather twisted liking of him. This is an interesting characterization of him. I've always regarded Aizen and Ichimaru as closer comrades rather than suspicious allies, but that's interesting too. I like his calculating nature in this piece.
Sweet beans! You almost made me like Aizen. That is a feat. I don't dislike him instinctively, but because people like him must be annihilated for the public good. But he is fascinating, and you gave us a peek into his inscrutable mind. And I like how you showed his awareness of Gin's basic untrustworthiness. I don't see any way that those two can really trust each other.