I don’t think anyone could have guessed that Unohana’s greatest pleasure was battle. Like Zaraki, she only finds true joy in fighting worthy opponents, of which she found in Zaraki as his strength grows to surpass hers. She’s a diabolical character, and the bankai she reveals looks truly vicious: a thin dark blade raising a curtain of what seems like blood. The actual nature of her bankai seems to be made intentionally vague however, and I can only speculate at what it actually does. After she releases it, their flesh begins to melt away, leaving just skeleton. In the very next page everything is back to normal, so perhaps this is the final stage of her “training” – destroying and cleansing Zaraki so that he breaks off his restraints and rises up with his true power. It would be befitting of the meaning of the name of Unohana’s zanpakuto, Minazuki.
All things are pointing to the conclusion of this fight, but we left off with a cliffhanger as usual. While it’s clear that Unohana is willing to sacrifice herself to unlock Kenpachi’s full strength, I’m sticking with my hope that both of them will make it out of this alive – honestly there’s no reason they can’t, especially with the healing abilities that she has demonstrated so far. Plus, teasing us with her bankai then not revealing what her real zanpakutou abilities are would just be unfair. It seems overly dramatic for Kyouraku and Unohana to decide that it is necessary for one of them to die, especially given that Soul Society needs them both badly. Although she has already given her farewell monologue, other characters have gone through worse and still lived, so I’m hanging on to hope that she will return to the 4th squad, ready to use her killing skills on the Vandenreich.