Not surprisingly, Zaraki is quickly overwhelmed by Unohana as she effortlessly evades his strikes and wounds him multiple times. Along with her katana, Unohana also uses some small blades for combat, possibly as a throwing weapon, and her tactics are brutally effective as she soon has Zaraki backed in a wall with a blade at his throat. Zaraki clearly respects her alot (likely the only person he ever respected and feared) due to her sheer combat prowess, to the point that he sheds tears. Of course the whole thing would be rather meaningless if he was killed right there, but at one point it does seem as if Unohana had run her sword through his throat. Zaraki notices this as well and possibly loses consciousness, but in the next moment his own sword is back in his hand, blocking Unohana’s blade. Given the consistency of the location of the blood splatters on her face, I don’t think this was just some trick of the mind. I’m guessing this is all part of the “training”, as Unohana is somehow forcing him back from death as a way to make him stronger. In her inner monologue, she cryptically mentions his oversight over her “sin”, which could be some mistake she made in the past that’s related to how he’s able to return from the dead. Without further explanation it will be hard to judge exactly what’s going on, but I am really, really praying that neither of them will actually die; it doesn’t help that Isane is grieving as if the note from Unohana was a farewell. Either way, I’m glad that their fight was not skipped over, and I hope that more of it will be shown.