Shukai (主解, Mastered Release) is the third and final upgraded form of the Zanpakutō. It is the form of the Zanpakutō that displays both the Shinigami and the Zanpakutō's true form and power. Like with Bankai, the Zanpakutō recieves a new name based on its upgraded abilities. However, unlike with Bankai, the Shinigami themselves also recieves a new name.
According to Soul Society legend, thousands of years before the Gotei 13's foundation and the rule of a Spirit King, a line of Shinigami existed that possessed the inborn ability to use Shukai; an ability beyond the traditional final form of the Zanpakutō — Bankai. It seems a user of Shukai appeared around the time the three planes of existence (the World of the Living, Hueco Mundo, and Soul Society) lost their balance of souls. The Shukai users have saved the worlds from the disaster caused by this imbalance each time.
After the formation of the Gotei 13 and the current order of the Spiritual World, Shukai users stopped appearing and, over the centuries, began to be regarded as merely a myth. However, shortly after the foundation of these spiritual organizations, a woman from Rukongai gave a prophecy of a "final" Shukai user that would come into existence and once again stop a calamity from befalling the universe.
Ōetsu Nimaiya, the first user of Shukai, and the creator of the form as the Zanpakutō's creator, disavows the genetic lineage of Shukai, claiming that it is only a coincidence. Shukai is only reserved for few Shinigami because of its strict requirements. Being the form beyond the Bankai, the first and most noticeable difference between Shukai and Bankai is the power increase. Similarly too how Bankai is ten times more powerful than Shikai, Shukai is ten times more powerful than Bankai (one hundred times more powerful than Shikai). Ōetsu notes that both Shinigami and Zanpakutō, upon achieving Shukai, stand on a plane high above other Shinigami and Zanpakutō.
Keeping true with its name (mastered release), the Shukai is the completed form of both the Shinigami and Zanpakutō. Ōetsu has noted that, no matter what form the Zanpakutō previously took, a Shukai will always take the form of a weapon that magnifies the power of the Shinigami's ability to the fullest. For example, Raian Getsueikirite's Shukai takes the form of a large war fan, as his ability is wind. According to Ōetsu, the weapon in Shukai is literally the manifested form of a Shinigami's soul and, therefore, unlike Bankai, cannot be broken by any means. Additionally, the abilities in which the Zanpakutō wielded in both Shikai and Bankai are mastered to finality.
Like with Bankai, in Shukai the Zanpakutō gains a new, longer, name which reflect its new abilities and personality. Unlike in previous release forms, however, the Shinigami themselves actually receives a new name, reflecting the very nature of their soul.
Unlike Shikai or Bankai, Shukai's release seems to be finite. After usage, the Shinigami who used it eventually loses the ability to use it ever again. While this time varies between users, it was shown that four months after his first usage of Shukai, though he had used it several times within this gap, Raian had lost his Shukai completely.
- Achievement of Bankai: The wielder must have achieved and mastered their Bankai forms.
- Materialization of Bankai Spirit: As with the achievement of Bankai, the wielder must be able to manifest the physical spirit of their Zanpakutō's Bankai within the real world.
- Genuine Affection for the Zanpakutō: Ōetsu has stated that Shinigami such as Suì-Fēng, who is known to hate her Bankai, are genuinely incapable of preforming Bankai. In the same manner, Shinigami such as Ichigo Kurosaki are also completely incapable of obtaining Shukai, due to the fact that he does not possess true love for his Zanpakutō. He claims that it is this requirement that makes Shukai such a rare release, as it is truly rare that a Shinigami feel a genuine connection to one's Zanpakutō.
There is only one method of Shukai obtainment. It is known by only by Ōetsu Nimaiya and can only be administered by him in the Royal Palace city of Tenkyūden. The ritual is known as the Ketsurui (血涙, Tears of Blood) and takes place at the Kōruihora (紅涙洞, Cave of Bitter Tears).
- Using the unique powers of the Kōruihora, the Zanpakutō spirit, in its Bankai state, is completely split from the Shinigami, making them two completely separate beings. Following this, a unique Reijutsu is activated, materializing the supreme fears of the Shinigami and the Zanpakutō into a mirage, which takes the form of a single entity; the culmination of their fears and nightmares.
- Both the Shinigami and the Zanpakutō then must defeat this entity. However, there is a catch; the entity is incapable of being defeated unless the Zanpakutō and the Shinigami are completely synchronized emotionally and are united in a single purpose. According to Ōetsu, this is another reason that Shukai is impossible for Ichigo Kurosaki, as both Ichigo and his Tensa Zangetsu have different things they want to protect. In order to defeat this dark entity, both the Shinigami and their Zanpakutō must learn each others strengths and weaknesses and fight together as one entity, despite being physically separate, and be united in their desire, in order to defeat the darkness within. Ōetsu explains this better by saying they must be like two rivers that merge perfectly and become indistinguishable from one another.
This ritual is extraordinarily dangerous and deadly. Once started, Ōetsu is incapable of stopping it, regardless of the outcome. To survive, the Shinigami and the Zanpakutō must kill the dark entity that results from the ritual, or face death themselves.
Appearances in Other Media
According to the author, Shukai will have a major role in Bleach: Reverse of the Moon.
- The members of the Getsueikirite Family are noted to have a particular affinity for this ability.