In addition to zanpakutou are cool, I will also add that Ichimaru, individually, is also very cool. He just like, saunters his way into the story, speaking Kansai, dismembering people, and demonstrating very specific knowledge of Ichigo's hair color:

I think this sounds less bananas in Japanese than it does in English, because that's just what that color is called in Japanese, but the phrase has roots in Genji and to me it still feels like the equivalent of someone using Crayola colors to reference things ("burnt umber" instead of "reddish brown"). Amazing, for multiple reasons: That Ichimaru would describe Ichigo thusly, in this moment; that he's referencing official Gotei intel that likely also called Ichigo daylily-colored.

I say official Gotei intel and not just secret Aizen intel, because I think Ichimaru might be referencing the same Onmitsukidou report that Byakuya talks about in Chapter 54:

[Bleach 054]

(Did Byakuya need to be that specific about this information? Did he need to bring it up at all? No he did not, but Byakuya be Byakuya-ing. Anyway--)

After Byakuya and Renji's encounter with Ichigo, the Gotei is able to put a name to a face, and maybe even gain additional insight into the nature of Rukia's crimes. I'd never really thought about it before, but if Rukia's High Crimes (overstaying her welcome in gigai/in the Living World and sharing her powers with a human) have the real, tangible impact of some weird daylily-colored guy showing up to invade the Seireitei, I could see an argument being made for her execution/her accelerated execution. I don't think most of the people who go off to meet the Ryoka Invasion have put all of these things together or really care to (but maybe I'll be proven wrong on re-read; guess I'll sit tight until Chapter 81 to see what our very first CAPTAINS' MEETING, MY BELOVED has to say), but that actually does make some sense to me. I'm not saying I agree with the justification for Rukia's execution, lol, but like, yeah, that could track?? I see it??

It also makes me think about why Ichimaru shows up in Chapter 65 to poke Byakuya. I've always figured it was just to poke him, because "I just wanted to poke Byakuya" is very relatable and convincing in itself. But in addition to the whole Rukia Thing, and Aizen et al being involved in the Rukia Thing, Ichimaru's comments make me also feel like he was looking for more information about Ichigo, specifically, seeing as Byakuya recently experienced him first-hand. Presumably, Byakuya just finished writing his report. Did Ichimaru want that info before it even went to press, fresh from the horse's mouth? Or maybe he wanted to intercept the mail so he could be the first to read it.