Zanpakutō

A  is a fictional type of weapon in the Bleach series wielded by those with shinigami powers. The art of using a zanpakutō is called zanjutsu (swordsmanship).

Overview
Most zanpakutō look like regular katana, with slight variations between them as one would expect between different swords. However, each zanpakutō is imbued with a unique sentient spirit, which gives the sword the power to send pluses to the afterlife, purify hollows, and transform the zanpakutō itself into more elaborate and powerful forms. To facilitate these tasks, zanpakutō have unique abilities that match their owner's characteristics.

A zanpakutō spirit are part of its owner's soul, and often share the same personality traits. At the same time, however, they are also independent, and thus can be considered a shinigami's partner in battle. Because they are part of their owner's soul, a zanpakutō cannot be replaced, though it will slowly regenerate if broken. As a shinigami gains power, their zanpakutō can change form by allowing the inner being to manifest itself to a greater degree in the outside world. The sword and the inner being are synonymous to each other. No matter what form (or size) a zanpakutō takes, it is always virtually effortless for its owner to wield because it is a part of its owner's soul. On the other hand, it is much more difficult for a shinigami to wield a zanpakutō that is not their own, though Kaname Tōsen is the only character in the series to actually do such a thing.

Forms
Depending upon the shinigami's ability to communicate with and control their zanpakutō ' s spirit, a zanpakutō can manifest itself in two additional forms and revert to a sealed state. These two forms, known as shikai and bankai, 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, are unable to seal their zanpakutō and therefore carry them in released form constantly.

In addition to the upgraded forms, the sealed form of a zanpakutō can also be radically altered, though such alterations are purely cosmetic and usually don't offer any significant advantage in battle; one exception is Ikkaku Madarame's Hōzukimaru, whose hilt stores a blood-clotting ointment. Shinigami with great spiritual power and who are unable to control it have larger zanpakutō, as Ichigo Kurosaki did when he first became a shinigami. Isshin Kurosaki, Ichigo's father, explains at one point that high-level shinigami must be capable of maintaining and suppressing the size of their sword. Otherwise, they would end up swinging around swords the size of skyscrapers. Zanpakutō can also be disguised as other objects, though such objects seem to need to be of similar proportions to the sword itself. Both Kisuke Urahara and General Yamamoto, for example, disguise their zanpakutō as canes.

Shinigami who are unable to communicate with their zanpakutō wield a nameless version known as asauchi.

Shikai
The 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 already has its own name. Therefore, the shinigami must be able to communicate with their zanpakutō effectively, which requires being able to speak to the spirit within its world. Achievement of the shikai is a mark of control of a zanpakutō, and it appears to be a requirement for advancement within the shinigami ranks, as most (with the notable exception of Kenpachi Zaraki) seated officers and presumably all lieutenants are capable of shikai.

After first learning the zanpakutō ' s name, the shikai can be performed at will simply by speaking a command followed by the zanpakutō ' s name. The command varies between users and range from a simple imperative verb to a short poem. It often relates to the zanpakutō ' s signature ability, or hints at the nature of its spirit. This step may be bypassed by expert shinigami who have learned how to use their bankai. In rare cases, a zanpakutō, once released, will remain in that state indefinitely. Such zanpakutō are described as a full-time released form type, such as those of Ichigo and Zaraki.

Once the shikai is activated, the zanpakutō will change form to access whatever special abilities it is capable of. They usually remain in the form of a sword, but the type of sword differs radically among various zanpakutō. The special abilities of the zanpakutō, like the zanpakutō itself, have specific names that usually must be announced to fully activate the effect. As Ichigo's zanpakutō, Zangetsu, explains, knowing the name of an attack and not knowing it makes a difference in the amount of power that attack has.

Bankai
The is the second and final form of a zanpakutō. To achieve it, one must be able to materialize their zanpakutō ' s spirit in the real world and subjugate it, giving the shinigami full reign over the zanpakutō ' s power. According to Yoruichi Shihouin, the power of bankai typically increases a shinigami ' s power by a factor of ten. Because such an act usually takes hundreds of years of combat experience to achieve, it is rare amongst shinigami and almost exclusively limited to the thirteen shinigami captains in the Gotei 13. Byakuya Kuchiki claims that among the four noble houses of Soul Society, only one person in several generations will be born with the spiritual power necessary to achieve it. Ichigo Kurosaki and Kisuke Urahara are exceptions to this fact. Using a special device created by Urahara, which forcibly materializes a zanpakutō spirit (thus bypassing the experience portion of the training), they were able to attain their bankai within three days, instead of the normal hundreds of years.

After a shinigami is able to materialize and subjugate their zanpakutō ' s spirit, the zanpakutō can assume its final and most powerful form. Unlike the shikai, there is no command phrase to activate bankai, though the user will usually say "bankai" beforehand. A zanpakutō ' s bankai is often a manifestation of the spirit itself, usually creating a massive creature or effect to aid the user in battle (Ichigo's bankai is an exception, becoming more compact instead). The bankai itself will receive a different name from the ordinary zanpakuto (Ichigo's Zangetsu becomes Tensa Zangetsu, Byakuya's Senbonzakura becomes Senbonzakura Kageyoshi). Certain shinigami also change with their zanpakutō, gaining clothing similar to what their spirit form looks like. Most zanpakutō will also gain additional special abilities. Like with the shikai, most of these abilities have an associated name. Maintaining the bankai is taxing for the wielder, and it is difficult to maintain it for long periods of time.

Resurrección
Arrancar, which are hollows that have removed their masks and gained shinigami powers, have zanpakutō and can perform something similar to a shinigami ' s release called resurrección (Spanish for resurrection). Unlike shinigami zanpakutō, however, an arrancar's zanpakutō is simply the arrancar's hollow powers sealed into sword form. By releasing their zanpakutō in the same manner as a shinigami, an arrancar can release their hollow powers.

Because their powers are sealed in their zanpakutō, an arrancar's release will usually transform some or all of their body into a hollow-like form, allowing them to use their abilities freely. This form usually reflects what the arrancar looked like as a hollow, though this is not always the case; Grand Fisher, for example, looks vastly different in his resurrección form than how he appeared in his original hollow form. Arrancar normally only return to their human form when they reseal their hollow powers; doing so without resealing, though possible, is a permanent change comparable to amputating a limb. The reason arrancar go through such trouble to seal their power is twofold: it allows them to maintain human form and conserve their power in times of inactivity.

Types
There are several types of zanpakutō, classed by the main purpose or effect of their special abilities. For example, Ichigo Kurosaki's zanpakutō is a melee-type zanpakutō, since it is primarily designed for close-combat. Yumichika Ayasegawa's zanpakutō, on the other hand, is a kidō-type zanpakutō, since it's designed around its special ability rather than its close combat potential.

Some zanpakutō are also classified by element: Tōshirō Hitsugaya and Rukia Kuchiki possess ice-type zanpakutō, Shigekuni Yamamoto-Genryūsai controls a fire-type one, and Kaien Shiba's uses water-based abilities.