Bankai (卍解, Final Release) is the second and final upgraded form of a Zanpakutō. Prior to Ichibē Hyōsube giving this form its name, it was known as a Shinuchi (真打, Headliner), and when a Shinigami achieved it, they would possess an "Evolved Zanpakutō" (進化した斬魄刀, Shinkashita Zanpakutō).[59] To achieve Bankai, one must be able to materialize and subjugate their Zanpakutō spirit. Materialization means the opposite of getting dragged into the Zanpakutō's inner world: the wielder needs to summon the Zanpakutō's spirit into the physical world. It usually takes 10 years or more to achieve, plus the experience needed to master it.[60] Despite the Zanpakutō spirit being subjugated for their Shinigami to learn Bankai, the Zanpakutō also becomes stronger and learns Bankai at precisely the moment their Shinigami learns it.[61] Even though Bankai is the final stage of a Zanpakutō, it does not mean the Shinigami's growth ends there. A Bankai, especially one recently obtained, can evolve even further as its Shinigami gets stronger.[62]
The power and forms of Shikai and Bankai are dependent on the Zanpakutō, and vary according to the wielder's strength and training. But in general, one's power can grow 5 to 10 times greater by attaining it.[63] Only the strongest Shinigami can use it, and it is the ultimate technique of a Zanpakutō. Even the four noble families, whose members are always exceptionally talented, only have a member capable of Bankai every few generations. Those who achieve Bankai always have remarkable roles in the history of Soul Society.[64]
Ichigo Kurosaki and Kisuke Urahara are the only known individuals who have attained Bankai through a far shorter, yet much more dangerous method. Using a special device created by Urahara, which forcibly materializes a Zanpakutō spirit (thus bypassing a large portion of the training), they attained their Bankai within three days instead of the normal hundreds of years. After successfully testing the device and achieving Bankai, Urahara stated training by using this method for more than three consecutive days could prove to be fatal, which is why Ichigo was forced to achieve his own Bankai within three days.