Unohana made the decision to come forward as the first Kenpachi and battled Zaraki in a brutal combat, repeatedly killing and reviving him until he unlocked his true powers, which had lain dormant for ages. This was essential for the Shinigami to successfully combat the Quincy since Zaraki Kenpachi’s genuine abilities turned out to be a deciding factor in the Shinigami’s favor.
Why did Kenpachi Zaraki kill Retsu Unohana?
We need to describe the events that led to their battle as well as how the fight transpired in order to fully comprehend why Kepnachi killed Unohana. This section of Kubo’s story contains the answers we seek, thus it is important to read it through because doing so is the most effective way to find them.
Unohana is appointed by the Central 46 to oversee Kenpachi’s zanjutsu training after he loses to the so-called Yhwach Royd Lloyd. She claims that as the First Kenpachi, she is the only one who can defeat him. Following the encounter, Unohana writes her Lieutenant Isane a letter in which she ostensibly announces that she will not be able to return.
When Unohana notices that Zaraki is approaching his breaking point, she decides to strike him and cuts his shoulder once more. The two Kenpachis then clash their swords once more. Zaraki is told by Retsu that he is quite weak and that people who use only one hand to hold their swords while the other is free don’t really enjoy the fight.
Zaraki reprimands her for stabbing him with a common blade rather than her Zanpakut and adds that such stunts demonstrate how much she has changed since the time he used to respect her. He hears Retsu Unohana yell at him that he shouldn’t speak like that during a combat after cornering him on a rock and putting him under her control.
While they are still fighting, Kenpachi keeps collapsing, but Retsu Unohana keeps tending to his wounds. Unohana is struck by a powerful strike from Kenpachi that changes the momentum of the battle. Unohana continues to tie Zaraki up after giving him the severe wound from Zaraki and striking him in the cheek.
Retsu asks Kenpachi if he really believed that she would die from such an attack before quickly healing the wound with the aid of her medical Kid. Retsu Unohana utters the name of her Bankai, Minazuki, and then releases her Bankai, covering the area in a thick curtain of black liquid.
Unohana bids Kenpachi farewell while getting his throat punctured with his Zanpakut, leaving Zaraki as the victor of the crucial conflict and the sole surviving Kenpachi at the time. Unohana is beaten after Zaraki’s Zanpakut impales him. Zaraki’s victory, but, is bittersweet because he begged Unohana not to risk dying at his hands. In the midst of Unohana telling Zaraki that he was the only person who made her happy during the conflict, Zaraki connects with his Zanpakut’s spiritual side, which is willing to reveal its name.