The initial release (始解, shikai?) is the first "upgraded" form available to a zanpakutō. To activate it, the shinigami needs to learn the name of their zanpakutō. This is not as simple as simply picking a name, as the living spirit of the zanpakutō chooses its own name. Therefore, the shinigami must be able to communicate with their zanpakutō effectively. Achievement of the initial release is a mark of expert control of a zanpakutō, and it appears to be a requirement for advancement within the shinigami ranks, as most seated officers and presumably all lieutenants are capable of the initial release.
After first learning the zanpakutō's name, the initial release can be performed at will simply by speaking a command followed by the zanpakutō's name. The command phrase varies between users and often relates to the zanpakutō's signature ability, or hints at the nature of its spirit. This step may be bypassed by expert shinigami, usually those who are at least approaching discovery of their final release.
In rare cases, a zanpakutō, once released, will remain in that state and will not have a sealed state. Such zanpakutō are described as a full-time released form type.
These two forms, known as the initial release and the final release, are akin to "upgrades" for the zanpakutō, giving it abilities far beyond that of its simple use as a sword.
Shinigami usually carry their zanpakutō in the sealed state and activate the released forms as necessary. Shinigami with zanpakutō of the constant-release type, such as Ichigo Kurosaki and Kenpachi Zaraki,[1] are unable to seal their zanpakutō and therefore carry them in released form constantly.