Zanpakutō Spirit/Anime Continuity

A is the spirit embodying a Shinigami's Zanpakutō that resides within their master's inner world.

Overview
A Zanpakutō Spirit is a part of their Shinigami's soul, and their appearance and abilities are a reflection of this; as such, they also share their master's resolve. They exist in tandem with their master; they are born alongside their Shinigami, and die with them. A Zanpakutō Spirit's power is separate from that of their owner, and when a Shinigami draws on this power in addition to their own, their Zanpakutō will become even stronger. They dwell within the inner worlds of their Shinigami masters.

Communication
Communication with one's Zanpakutō Spirit is essential for a Shinigami's growth. The most common method of communication between a Shinigami and their Zanpakutō Spirit is called, where the Shinigami places their Zanpakutō nearby, enters a meditative state, and merges their mind with that of their Zanpakutō Spirit while entering their inner world. Alternatively, a Shinigami proficient enough in communicating with their Zanpakutō Spirit can do so instantaneously and without any preparations. However, a Zanpakutō Spirit can also pull their master into their inner world or manifest itself in the real world in order to speak with their master.

A lack of communication between a Shinigami and their Zanpakutō Spirit can lead to the power of both being weakened and even prevent a Shinigami from releasing their Zanpakutō. Communication can be lost or prevented for several reasons:


 * Kōga Kuchiki's descent into madness led to the bond between him and Muramasa degrading over time, making it harder and harder for Muramasa to hear Kōga's voice and eventually preventing Kōga from releasing his Zanpakutō at all. By openly renouncing his ties with Muramasa, Kōga completely severed all bonds with his Zanpakutō spirit, making it impossible for Muramasa to hear his voice again when Kōga later called out for him.

Zanpakutō Rebellion
During the Zanpakutō Rebellion, a Zanpakutō Spirit named Muramasa manifested dozens of other Zanpakutō Spirits into the real world, claiming he intended to end the tyranny of the Shinigami over them. This led to numerous changes in the appearances, personalities, and powers of the Zanpakutō Spirits who were manifested this way.

Appearance
The Zanpakutō Spirits' physical appearances were radically altered by this event. Those with animal-like spirit forms gained humanoid bodies in the real world, with Zabimaru manifesting as a fur-covered woman attached to a snake-like boy by a chain and Hyōrinmaru manifesting as a green-haired man with a large scar on his face. However, all of them still possessed appearance traits correlating to their name and powers, as well as their master's personality and appearance. These changes left the Zanpakutō Spirits unrecognizable to most of their masters, requiring the Shinigami to attain confirmation by having their Zanpakutō Spirit reveal their name, witnessing their powers first-hand,  or performing a test of some sort to confirm their identity, although some Shinigami determined a Zanpakutō Spirit's identity from simply looking at them. The reason for these physical changes is unknown; Gegetsuburi blames Marechiyo Ōmaeda's physical appearance for his manifestation's large amount of body fat, but Suzumebachi claims she chose her manifested appearance because she did not like Suì-Fēng's "lame style".

Personality
Most of the Zanpakutō Spirits underwent a drastic change in personality upon manifestation because of the influence of Muramasa's brainwashing; they became destructive, merciless, arrogant, cruel, short-tempered, vain, and sadistic. However, some Zanpakutō Spirits did not gain these traits; Hyōrinmaru pursued his own goals and only fought others to determine whether or not they were his master, and Hisagomaru remained timid and gentle, though confused by his separation from Hanatarō Yamada. Additionally, all of the Zanpakutō Spirits shared certain personality traits and fighting styles with their masters.

Most of the Zanpakutō Spirits manifested by Muramasa did not like an aspect of their master or had a goal of their own, which Muramasa exploited in order to brainwash them:


 * Gonryōmaru left Chōjirō Sasakibe because he was frustrated with Chōjirō's lack of a presence in the 1st Division.


 * Suzumebachi left Suì-Fēng because she hated Suì-Fēng's devotion to Yoruichi Shihōin and inability to pay attention to herself.


 * Gegetsuburi left Marechiyo because he detested Marechiyo's appearance and braggart personality.


 * Tobiume left Momo Hinamori because she wished to become stronger and did not want to stay with someone who was as weak as Momo was.


 * Zabimaru left Renji because he had grown tired of Renji's weakness and wished to become stronger on his own.


 * Katen Kyōkotsu left Shunsui because they could not stand his arrogance.


 * Kazeshini left Shūhei Hisagi because he did not believe Hisagi truly understood him.


 * Haineko left Rangiku Matsumoto because she wished to lead a new and exciting life without Rangiku.


 * Hōzukimaru left Ikkaku Madarame because he hated how Ikkaku acted like a "badass" without having the skill to back it up.


 * Ruri'iro Kujaku left Yumichika because he detested Yumichika hiding his true power for the sake of remaining in the 11th Division.


 * Sode no Shirayuki left Rukia Kuchiki because she was resentful toward Rukia for not considering how she was effectively forcing Sode no Shirayuki to lend her power.


 * Zangetsu left Ichigo in order to determine who was stronger between the two of them.

After being defeated by their masters or having their brainwashing reversed by Mayuri Kurotsuchi, the Zanpakutō Spirits regained their original personalities, removing any animosity they held toward their masters. However, Zanpakutō Spirits who had killed their masters after manifesting lost their minds and became known as the Tōjū.

Powers & Abilities
The manifested Zanpakutō Spirits had the ability to manifest and release their sealed Zanpakutō form at any time, though some only summoned their Shikai instead of their sealed state. However, a few Zanpakutō Spirits used weapons other than their Zanpakutō forms in battle:


 * Gonryōmaru wielded a long pike.


 * Suzumebachi wielded a large stinger on her right arm that possessed the same power as her Shikai form did.


 * Tobiume used two large bells connected by a long sash to throw fireballs at her opponents.


 * Tenken wielded a pair of bolas.


 * Sōgyo no Kotowari used a large scroll and a pair of fans for various attacks.

Additionally, some Zanpakutō Spirits displayed the ability to manipulate an element that their Zanpakutō form could not:


 * Tenken possessed the ability to generate fire along his weapons.


 * Kazeshini displayed the ability to use wind in his attacks and transform into a tornado.


 * Sōgyo no Kotowari could use their fans to fire bolts of lightning.

As the embodiment of their sword form's power, the manifested Zanpakutō Spirits possessed absolute control over their own power, in some cases displaying greater proficiency at using their techniques than their masters did:


 * Zabimaru's Hihiō Zabimaru possessed no blind spots.


 * Hyōrinmaru could use techniques of his Bankai form with his Zanpakutō form still sealed.


 * The range of Sode no Shirayuki's Some no mai, Tsukishiro was not limited to the area within her sword swing.

Effects of Manifestation
The manifested Zanpakutō Spirits leaving their swords had a dramatic impact on the Shinigami. At first, they simply could not communicate with their Zanpakutō, but within a day of the manifestation, no one could release their Shikai. This left many Shinigami unprepared to fight without the aid of their Zanpakutō's special abilities, and forced them to develop new fighting styles in order to compensate for this loss. Though Shinigami could regain access to their Shikai upon strengthening their resolve, they remained unable to activate their Bankai until they defeated their Zanpakutō Spirit in combat.