Yonkō

The Yonkō (四侯, Four Leaders) is a shitennō title given to the four most powerful Shinigami Captains of the Gotei 13. Similar to the passing of the Kenpachi title, a Yonkō would obtain the title by killing (or simply defeating) the previous titleholder.

Overview
The four Yonkō are meant to correspond to the four basic Shinigami combat skills: Zanjutsu, Hakuda, Kidō, and Hohō. This is because each Yonkō is said to be an almost unrivaled master of a respective field of combat. It is not uncommon for a Yonkō to also hold the title of Kenpachi, as Kenpachi Kuruyashiki was the predecessor to Hikaru Kurosaki, and Raian Getsueikirite himself was also a Kenpachi.

Formation
According to legend, the Yonkō's origins precedes even that of the Gotei 13, as the first Yonkō to have been Captains in the Gotei 13 were among the fifth generation.

Titleholders
Note: Titleholders are arranged in chronological order by way of possession of the Yonkō title. † means confirmed death.

First Generation
Little is known about the First Generation of Yonkō beyond that they were the first to hold the title of Yonkō, revered as "Gods" among the people. According to legend, the four original Yonkō consisted of a Kawahiru, a Kurosaki, an Asakura, and a Getsueikirite. Two members of the Rekishi no Ban'nin were assigned to record the deeds of the Yonkō. Pandaga, the elder of the two historians, died during one of the Yonkō's battles. Afterwards, Lavi Kawahiru, a member of the Kawahiru's lesser house, traveled with the Yonkō.

Kurama Kawahiru claims to have been one of the Yonkō of the first generation. Little is known about the Kurosaki member of the First Generation beyond his title as the Akagami. Records show that Shūshi Gensaku Kaenōra, a member of the 6th generation of the Yonkō, was a contemporary to the first generation of the Yonkō, and that he was a candidate for a Yonkō title. However, when the time came, Gensaku's mastery of Reiseī could not compete with the talent that G.G. Roadraid the Blade demonstrated.

Second Generation
Nothing much is known about the Second generation of Yonkō. It is said they were the last to be composed primarily of Sōzōshin, as the Grand Migration had later occured during this time. It is also the first generation to have females in the Yonkō. The two females specialized in combination attacks, thus their monikers as the Aoitsuki (Blue Moon) and the Akaitsuki (Red Moon). In addition, this is the only known generation of Yonkō to have intermarried. The 2nd Generation of Yonkō were also the first users of Reiseī as they were all students of Shūshi Reiseī I.

Third Generation
Nothing much is known about the Third generation of Yonkō, other than that it was the first to be comprised solely of Shinigami with no variations in their powers.

Fourth Generation
Not much is known about the Fourth generation of Yonkō, other than that Shōyō Shakyamuni and Hanzei Kurosaki were titleholders among this generation. It is also said that Lavi Kawahiru of the Rekishi no Ban'nin who recorded the adventures of the Third generation of the Yonkō also chronicled the deeds of the Fourth Generation.

Fifth Generation
Not much is known about the Fifth Generation of Yonkō, other than they were the first among the Yonkō titleholders to become Captains within the Gotei 13. However, only one of their number, Rai Kurosaki Getsueikirite, did not become a Captain of the Gotei 13 even though he saw it form in his lifetime. Rai was also the oldest member of the Yonkō at this time, which could have made him a contemporary of the Fourth Generation. It is heavily implied that Kamui was once a Yonkō of this generation. In addition, Chiyome Mochizuki was also a Yonkō and recorded as the youngest Yonkō in history, attaining her title when she was in her late teens. Due to his age, Lavi Kawahiru was accompanied by his assistant, Joan Kurosaki, when recording the Fifth Generation's acts.

Sixth Generation
Not much is known about the Sixth generation of Yonkō. Shūshi Gensaku Kaenōra, a member of the Kaenōra Clan, was the first of his clan among the Yonkō's ranks. They were the last generation whose deeds were recorded by Lavi Kawahiru and Joan Kurosaki as Lavi passed away during his travels with the Yonkō.

Seventh Generation
Not much is known about the seventh generation of Yonkō. The son of Shūshi Gensaku Kaenōra, Shūshi Musokuno Kaenōra, was a member of the seventh generation of the Yonkō. This was the only instance where a Yonkō title was directly passed from father to son. Kenpachi Kuruyashiki was a member of this generation. Joan Kurosaki was the only member of the Rekishi no Ban'nin to record the deeds of the Yonkō in this generation. Near the end of the Seventh Generation's time, Joan was killed in battle and her records were supposedly destroyed. Lore says that Joan kept perfect indestructible copies of her records somewhere in the Seirietei as to not lose her work.

Eighth & Ninth Generations
"That's because you're acting like a child. If Hikaru-san or Echo ever said the same to me, I'd punch them out too. That's our relationship, isn't it? If one of us went down the wrong path, the other three would punch him out. That's how it's always been... That's why we'll be able to always stay on the right path. Always, always forward. Whatever space you dug between us is not my problem... That's your problem. No matter how many times you cross the line... I will beat the shit out of you as many times as it takes! You don't get to meet many people like this in life. We're rather lucky... to have made such idiotic friends like them, huh? Raian, if I should ever walk down the wrong path, then it'll be your turn to knock some sense into me."

- Seireitou Kawahiru, after punching Raian Getsueikirite

Possibly the most noteworthy "modern" generation of the Yonkō, these four Captains fought together in the First Shinigami-Arrancar War. The reason they are classified as both the eighth and ninth generations is that, while Seireitou, Hikaru, and Hibiki were originally the Eighth Generation, along with Ryun Seijūrō, they had never passed down their titles prior to their defection, save for Ryun. Raian, becoming the Captain of the Tenth Division several centuries later, would be the sole holder of the Yonkō title still employed as a Gotei 13 Captain.

They are respectively: Each were almost equal to each other in power, and the group had no real leader. Reasons for this were, as stated by Hikaru: "We fight knowing that our backs are covered. To elect a leader would be inefficient. That, and if we tried to choose a leader, we'd need a planet bereft of life in order to 'negotiate'." Though they did cooperate on some occasions, the four Yonkō of these generations maintained major rivalries with each other.
 * The Shiroyasha (白い悪魔, White Demon)
 * The Hitokiri Urufukuro (殺人者黒狼, "Urufukuro the Manslayer"; literally Man-Slayer, Wolf of Darkness)
 * The Aoshime (青死目, "Death of Green Eyes")
 * The  Baragaki no Karite (刈り手死去, "Thorn-like Reaper"; more commonly known as "Baragaki no Raian")

Despite working at one time together, Seireitou has explained that they are each others "greatest allies" and also each others "fiercest enemies". Perhaps the most prominent rivalry in the group is Seireitou and Raian's rivalry. The two are very close friends, and respect each other the most, but have a deep rivalry with one another, that leads to climactic battles, often damaging large portions of their surroundings. In addition, there are the more less touched-upon rivalries, such as the one between Seireitou and Echo. Unlike any of the other Yonkō rivalries, Seireitou and Echo's seem to be born out of a deep disdain and mistrust for one another. Both think they are superior to the other, which only fuels their tendency to fight each other. Hikaru and Echo mostly have periodical doctrine arguments, but this has never been considered a rivalry; more of a live and let live relationship. "I never took up this title because I wanted to look down at everyone else. None of us did. The purpose of the Yonkō was never to be some sort of exclusive club. We fight for the defense of all worlds,,, and even the s. We stand not as emperors or kings. We stand as soldiers fighting on behalf of our people to ensure a world of tranquility. That is what I have always believed, and that is why I cannot stop fighting people who preach peace, but really mean to bring injustice and suffering to the world. And that is why I cannot lose to you, a man with Hell envisioned for all worlds."

- Hikaru Kurosaki speaking to Rekishi Riraita

Seireitou once viewed Hikaru as an obstacle he had to surpass in order to realize his true potential. This rivalry seems to be one-sided, as Hikaru never shows much interesting in besting Seireitou in combat. Eventually, even Hikaru admitted to seeing a growth in Seireitou following the events of the War, although claiming that he "hadn't changed since back then." Since the Yonkō Reunion, Hikaru admitted that Seireitou has changed slightly from his old self, but not enough to make his friend a different person. Hikaru is also beginning to see Seireitou as something of a brother.

The Stooge Duo (ぼけ役種, Bokeyaku Nitane) was the nickname given to Seireitou and Hikaru, who were considered the more eccentric members of the four Yonkō.

This is the only generation of the Yonkō to have their history not recorded by a member of the Rekishi no Ban'nin. To compensate for this, Hikaru is known to keep a diary of his adventures with the Yonkō in addition to relying on the near-godly memory of his wife, Rukia, for other details he may have missed. His record is not considered an official history of the Eighth and Ninth Generations of the Yonkō.

Tenth Generation
There does not seem to be a tenth generation group of Yonkō even though all of the ninth generation were dishonorably discharged, reassigned, or left the service. Hikaru Kurosaki has stated that "there has not been a valid reason for a new generation of Yonkō to appear since the First Shinigami-Arrancar War." As such, the Ninth Generation of the Yonkō are considered to be the current generation.

Behind the Scenes
The term "Yonkō" can be considered a homage to the group of the same name from the series One Piece, although the translation used for this group is slightly different.