Muramasa

Muramasa is the spirit of Koga Kuchiki’s Zanpakuto and the main antagonist of the Zanpakuto Unknown Tales arc of the Bleach anime.

Past
A few hundred years before the events of Bleach, Muramasa was the faithful Zanpakuto of Koga Kuchiki. It was during that time that he used his power to put the Soul Society’s civil war in the Seireitei’s favor and whenever Koga was feeling underappreciated, Muramasa would console him. However this almost got to the point of overpraising his master and when Koga was framed for being a traitor, Muramasa drove him to seek out justice. But though the Zanpakuto spirit meant well, things turned out badly when his master killed the men responsible. This resulted in Koga having a breakdown as he realized that his life was over. As his master started to kill innocent people, Muramasa tried to voice his disapproval, only to be ignored. Finally Koga became convinced that everyone was jealous of his power and turned on the entire soul Society. He continued to seek deeper and deeper into insanity as he killed more and more people and even began abusing Muramasa. This cost Koga the ability to communicate with his Zanpakuto and use the sword’s power. Muramasa came to believe that his master had abandoned him and fell into despair.

Launching the Zanpakuto Rebellion
However Muramasa soon found out that Koga was actually just sealed away and began planning for his release. He started freeing the spirits of the Zanpakuto belonging to the captains and the lieutenants. Muramasa eventually gathered the ones he had released by that point in a cave and at this gathering, Haineko asked if they could leave. He told her they were waiting until they freed the rest of their comrades and then introduced them all to the freed Hyōrinmaru. Later captains, lieutenants, and other Shinigami of the Gotei 13 gathered on Sokyoku Hill, supposedly under the summons of Head-Captain Yamamoto. However Muramasa appeared and told them that Yamamoto would not be attending and that Zanpakuto spirits were free of them. After a short fight with all the Shinigami, he summoned a katana and stabbed it into the ground, generating an eruption of purplish flames that caused the peak of the hill to rise.

Encountering Hollow Ichigo
After Ichigo’s brief fight with Sode no Shirayuki, Muramasa appeared so as to prevent her from reuniting with Rukia. He showed his great power to Ichigo and it was then revealed he was a Zanpakuto spirit. Muramasa explained that he sought to free all Zanpakuto spirits from their “enslavement” to the Shinigami. His attempts to justify his actions only angered Ichigo and they engaged each other. At first the battle was evenly matched, but Muramasa used his powers to free Zangetsu from Ichigo, who took over the fight from Muramasa. However the Zanpakuto spirit was greatly surprised when Hollow Ichigo, taking advantage of Ichigo’s weakened state and lack of Zangetsu’s presence, took control of Ichigo’s body. Hollow Ichigo managed to take down Zangetsu, before Ichigo regained control and returned to normal. He fell unconscious and Muramasa became interested by him and used his powers to go into Ichigo’s inner world. When he refused to tell the Zanpakuto spirit about the power that had allowed him to defeat Zangetsu, Muramasa paralyzed Ichigo. He then forcibly called forth Hollow Ichigo, who found this all amusing. The Zanpakuto spirit noted that the inner Hollow’s powers increased Ichigo’s considerably and that they were like that of a Hollow. Muramasa then asked Hollow Ichigo what he is, besides another part of Ichigo’s soul and the inner Hollow said he was Ichigo’s purest instincts. The Zanpakuto spirit attempted to free Hollow Ichigo the same way he’d free the other Zanpakuto spirits, using a spell that forced them to accept their inner desires. However the inner Hollow was unaffected, much to Muramasa’s surprise and attacked him. The Zanpakuto spirit, curious about what an inner Hollow was, engaged him, but was forced on the defensive, when Hollow Ichigo demonstrated what a capable fighter he was. Realizing the inner Hollow was beyond his control, Muramasa used his powers to bind him in place. But before he could finish off Hollow Ichigo, Ichigo broke free of his own bonds and saved his inner Hollow. This surprised Muramasa and he asked why a Shinigami would save a Hollow, to which Ichigo responded by saying, he was a human, not a Shinigami. Muramasa was shocked even more when Ichigo forced him out of his inner world with only his spiritual pressure. Ichigo then swore to get Zangetsu back, but before he could attack Muramasa, Zangetsu reappeared and intervened. Ichigo managed to defeat his Zanpakuto spirit and Muramasa said he was surprised at his willingness to fight Zangetsu, but he stated he did this to honor their partnership. Suddenly Muramasa became extremely ill and transparent, which forced him to retreat. Afterwards the Zanpakuto spirit thought to himself that Ichigo might be important and decided to capture him by any means necessary so as to use his powers.

Unleashing Ryujin Jakka
Muramasa went to the Forest of Menos in Hueco Mundo and killed a number of Gillian Hollows. After slaying another Hollow, he killed and absorbed another one that he decided was powerful enough. Muramasa returned to the Soul Society via a portal that resembled a Garganta at the location of Ichigo, Momo Hinamori and Rangiku Matsumoto, who had just subdued Haineko and Tobiume. Muramasa began coughing and said he wasn’t used to this new body yet before being confronted by Ichigo once again. The Zanpakuto spirit attempted to use his spiritual binding powers, but due to being in a weakened state, it failed and he started to cough even more, as well as bleed from his eyes. Ichigo attacked, hoping to take advantage of Muramasa’s weakened state, but Senbonzakura blocked him. Byakuya Kuchiki ended the confrontation and left with the Zanpakuto spirits. Later, when Byakuya, at Senbonzakura’s request, killed Sode no Shirayuki, Muramasa sent him to return the broken Zanpakuto to its owner. He sent most of the other Zanpakuto spirits as backup and eventually a battle with the Shinigami resulted. After Byakuya returned, Muramasa received a communication from a Hell Butterfly. This resulted in the captain asking him if he planned to go to the Human World and the Zanpakuto spirit showed him Head-Captain Yamamoto, sealed by three Zanpakuto spirits. After explaining Yamamoto’s seal, Muramasa told his allies to be prepared for another fight with the Shinigami. Later, when the Shinigami arrived at the spirits’ base, Ichigo discovered the barrier holding Yamamoto. Muramasa appeared and fought Ichigo and managed to get him angry enough to use his full power. He unleashed an ultimate Getsuga Tensho, but Muramasa managed to merge with it for a moment then send it at Yamamoto’s barrier. The barrier was destroyed and Yamamoto awakened, however it was revealed that he’d created the barrier himself. He’d done so to prevent Muramasa from gaining control of Ryujin Jakka. Muramasa had launched the Zanpakuto Rebellion so as to find a power capable of destroying the barrier, finding it in Ichigo. The other Zanpakuto spirits were enraged to find out that Muramasa had just been using them and they angrily attacked him. But he’d already gotten control of Ryujin Jakka at that point and used it to destroy the cave and the other spirits. Muramasa then vowed to use this new power to destroy the Soul Society.

Freeing Koga
With help from Byakuya, Muramasa traveled to Karakura Town, planning to use the knowledge he’d found in Yamamoto’s inner world in order to free his former master, Koga. Upon arriving at the location of Koga’s prison, Orihime Inoue came across Muramasa and he attacked her, only to collapse. Orihime healed him, giving him back much of his lost strength, and remarked that his spirit energy was much like that of an Arrancar. Yatsuora Sado and Uryu Isida attacked Muramasa and maneged to hold their own, due to his wavering power. However Senbonzakura appeared and aided the Zanpakuto spirit, allowing him to make his way to Koga’s seal. Muramasa then recited a spell to free his partner and at first, he was overjoyed to see Koga again. However the Zanpakuto spirit was shocked when his master stabbed him upon awakening. Koga stated that it was punishment for abandoning him when he needed him, which led to his imprisonment. Muramasa realized that they couldn’t communicate because of their disharmony, not because Koga had given him up. Koga swore to kill his former Zanpakuto, unable to realize the truth himself. However Byakuya stopped Koga at the last moment and he decided to fight the Shinigami captain. Muramasa, still loyal to his former master, insisted that Koga use his power, but he scoffed at the idea. He said he was powerful enough on his own and destroyed the remainder of the sword. Abandoned and horrified, Muramasa fell into despair, sending his powers out of control and unleashing all of the Hollows he absorbed. Sometime afterwards, his despair and unstable power made his body collapse into a vortex. All the Hollows were sucked back into him and fused together, transforming Muramasa into a dangerous Hollow. He went on a rampage, attacking everyone he came across, but Orihime could see that the Zanpakuto spirit was still conscious inside, desperately trying to gain control. She also said that Muramasa was overcome by intense loneliness and anguish and just wanted to escape it. The Zanpakuto spirit finally succumbed to his Hollow side and Ichigo fought him. He succeeded in defeating Muramasa, but he refused to let all he worked for fail and transformed again. The Zanpakuto spirit became a huge and horrific dome-like being that engulfed Ichigo. Muramasa’s unstable energy created a Garganta, which summoned an enormous number of Gillians. The Shinigami and Zanpakuto spirits joined forces to close it and defeat the Gillians as Muramasa’s form began to grow more and more.

Final Battle with Ichigo
Within the structure was a manifestation of Koga’s inner world, which was an endless ocean with countless columns sticking out of it, Muramasa was surprised to see Ichigo there, but was delighted as well. Knowing that the Hollows he absorbed were destroying the inner world and he had only a limited time, Muramasa decided to finish his battle with Ichigo. He pointed out that the Zanpakuto spirit had no reason to fight anymore, but Muramasa said he was going to fight as long as possible. He used his spiritual binding powers on Ichigo, but he saw through the power and overcame it. Muramasa then used his illusionary powers, which gave him the advantage, but Zangetsu helped Ichigo. He gave him his eyes and immunity to Muramasa’s powers, allowing him to see through the illusions and overpower the Zanpakuto spirit. Ichigo finally realized the reason Muramasa was so bitter, he’d been deprived so long of the simple ability to talk his partner, the way other Shinigami and Zanpakuto did. Muramasa refused to listen to Ichigo, but Ichigo said that the Zanpakuto spirit had been trying to make all Zanpakuto communicate with their partners, hoping to do so with Koga once again. Muramasa, realizing the truth, stated it was a futile dream, but Ichigo told him not to let what Koga said control his life. They charged each other for a final attack and Ichigo won, causing Muramasa to fall into the ocean in complete despair. However the Zanpakuto spirit was surprised when Ichigo dived in after him and saved him, then got the both of them out of the structure to safety. Muramasa then admitted to his mistakes and Ichigo said he could make up for them. After apologizing for his actions, the Zanpakuto spirit faded away, happy to have met someone who finally connected with him.

Powers
Muramasa possesses great spiritual power, enough to surprise Ichigo. He can create multiple, invisible spiritual threads that he can use to bind a person and use his spiritual energy to distort a person’s five senses to create illusions. Muramasa is a skilled swordsman, able to fight Ichigo evenly with one hand and can summon a version of his Zanpakuto form, which can generate a powerful energy wave. He possesses great speed, able to keep up with Shunpo experts, and is extremely crafty, a skilled strategist and manipulator. Muramasa can absorb Hollows to remain materialized in the world, to make up for a lack of a Shinigami master. He can also use a version of the Garganta, allowing him to move to and from Hueco Mundo. Muramasa's most powerful ability is that he can enter a person’s inner world and bend them to his will. He can use this to release the negative emotions of a Zanpakuto spirit and it allows the Zanpakuto to take control of the wielder’s sword arm, forcing them to attack others. Only by understanding how the Zanpakuto works and sealing one’s heart against it, can a person overcome this ability. Muramasa can also use this to turn the spirit of a Zanpakuto against the wielder and remove the spiritual bonds between them. The only way to regain the allegiance of a Zanpakuto spirit is for the wielder to defeat them in battle. This is no easy task since losing the spirit can prevent a Shinigami from even being able to manifest the Shikai form of their Zanpakuto and Bankai is impossible. After transforming into a Hollow, Muramasa gained even greater spiritual power, greater speed, and high-speed regeneration. He also gained the ability to fire highly potent Cero blasts and a barrage of Bala blasts from his hands.

Trivia

 * Muramasa’s name comes from a famous 16th century swordsmith, whose blades were said to possess unnatural bloodlust, refusing to be sheathed until they drew blood, even if it meant cutting their owners.