Fai said:
Kaien was actually REFUSING to become Ukitake's vice captain. for a long long long long long long time.
We even had that whole flashback with Ukitake and Kaien sitting and talking and Kaien saying that "ill repeat, I don't want to be your vice-captain" (if i remember the line correctly).
Yeah, I remember that part. At first I thought, the reason why Kaien declined the offer was, he thought that he wasn't ready enough to be a vice-captain. Even though he was considered a genius (he graduated after only 2 years), Kaien denied that fact. When Ukitake mentioned that Gin graduated from the Shino Academy in a single year, he was impressed and noted that he was even "further" from being a vice-captain. But I guess, with the situation right now, that Ukitake, being "somewhat" had hidden agenda...it's safe to assume that there's another reason for Kaien's actions at that time.