Board Thread:Improvements and Issues/@comment-33728110-20200803202155/@comment-33728110-20200804074642

Unohana becomes a skeleton at the same time as Kenpachi and becomes normal again as soon as he realizes that he was asleep (Ch.526 pg 8-9). Kaido has its limits, which is why Orihime was needed to heal people after the fight against Aizen. We don't see indication that Unohana is using kaido like we do at the beginning of the chapter. After that they never deteriorate again, even though we see them make more exchanges. Also, she performed her bankai because Kenpachi was actually able to nearly kill her, so she said it was time to get serious. It is never implied that she can no longer kill him with Zanjutsu, in their very next exchange she knocks Kenpachi to the ground from the force of their swords clashing (pg 7).

I can make a suggestion for the effect of her bankai, but my main point of this post is to point out that it isn't really that clear cut what her bankai is, by its depiction. You made a good assumption based on her shikai using acid, but I think the [bankai] liquid looks more like blood. I also think it's better to focus more on the themes of a sword than its physical properties. Minazuki is a shikai that can devour people and heal them, so I think maybe Unohana does something similar with her bankai. What if her bankai has the ability to revive (maybe even from death) who it cuts down?

1) Every time Kenpachi is killed by her we see that he awakens and is still in the middle of fighting her. (ch 524 pg 15-16)

2) We only actually see her use kaido when she is critically injured. She even states that she learned to heal HERSELF to enjoy fighting forever. (ch 526 pg 15)

3) She says she will kill him a thousand times if she has to. (ch 525 pg 14)

4) She states that she believes the power she obtained was for that particular moment and that the tip of the sword will always be pointed toward killing the next strongest or nurturing them. (ch 526 pg 15-16)