Summary
Unohana's revelation as the first Kenpachi called into question Zaraki's claim to the title. Since a Kenpachi must have killed the previous Kenpachi to inherit the title, no one could have properly inherited the title from her. Zaraki's defeat of Unohana in the Thousand-Year Blood War confirmed his claim to the title.
Kenpachi Zaraki is definitely one of the strongest characters in the series. Bleachas the holder of the title Kenpachi, the strongest in Soul Society. However, a surprising revelation is made in The Thousand Year Blood War unintentionally putting his ownership of that title into question, until he finally deservedly won it.
The title of “Kenpachi” is a tradition that dates back to the early days of the 13th Guards. It is a title given to the strongest Soul Reaper, but to attain the title, one must defeat and kill the previous title holder in a one-on-one battle. Kenpachi Zaraki is said to be the 11th person to hold the title of Kenpachi; very few other Kenpachi holders are known, and it is said that there can only be one Kenpachi per generation of Soul Reapers (which is approximately every 100 years).
Traditionally, this title has belonged to the captains of Squad 11, which includes Zaraki and his predecessor, Kenpachi Kiganjo.
The title of Kenpachi was never actually passed down.
The revelation of Kenpachi first puts all the others into question.
In Thousand-Year Blood War, when Retsu Unohana takes Kenpachi Zaraki to train in Bankai, it is revealed that she was actually originally called Yachiru Unohana, the first person to hold the title of Kenpachi. Unohana seems to have given up her bloodthirsty ways in exchange for the life of the healer in Squad 4, but that is not how the title works. In order for the next person to inherit the Kenpachi title, they must kill the previous title holder… except Unohana is still alive to this day, meaning the second Kenpachi never actually killed her to take the title.
Therefore, ownership of the title of the second Kenpachi is illegal. However, this has a ripple effect, meaning that everyone holds the title of Kenpachi because technically, Unohana never actually held the title – it remains hers as long as she lives. Unfortunately for Zaraki, this means that Kiganjo never actually held the title either, and killing him does not actually pass the title to him. It is only after Kenpachi Zaraki fights and eventually kills Unohana during their Thousand-Year Blood War training that the title is properly passed, ensuring that Zaraki is not the 11th Kenpachi, as he believed, but actually the 2nd Kenpachi.
Because the rules surrounding the passing of Kenpachi are so specific, it seems there is no way to relinquish the title without dying in battle. It is unclear what would happen if the current holder were to die to an enemy; the title could be passed to the next strongest, or the next captain of Squad 11, or it could even simply be the end of the tradition of having a Kenpachi. Since fans know very little about other Kenpachi, it is difficult to say exactly what would happen next in such a scenario. Regardless of other Kenpachi throughout history whose claims to the title are now in question, Zaraki, at the very least, has earned his claim to the title. BleachThe strongest Soul Reaper fair and square.
