User blog comment:Salubri/The Thousand-Year Blood War arc Plot Points/@comment-11051098-20131129205538/@comment-5551986-20131130115945

"(Ukitake) has undergone a bit of an internal change." - I think its something to do with him meditating or bathing infront of some weird lotus before the second invasion.

http://www.mangapanda.com/bleach/547/7