Zanpakutō Rebellion

The  is an event in which Muramasa, a Zanpakutō spirit, frees many other Zanpakutō spirits from their masters and starts a rebellion under the guise of wanting to free all Zanpakutō spirits from the control of Shinigami. In truth, he seeks nothing more than to free his master, Kōga Kuchiki, who was sealed away long ago.

The rebellion begins when Muramasa appears and begin freeing the many Zanpakutō spirits. The Shinigami begin to lose the ability to contact their Zanpakutō spirits. Muramasa leads the spirits to a confrontation with the Shinigami atop Sōkyoku Hill. The Shinigami, now unable to use their Zanpakutō, are unable to deal with their former Zanpakutō, throwing the Seireitei into a state of emergency.

The event ends after Ichigo Kurosaki enters the dome-like structure which an out-of-control Muramasa creates. Ichigo fights Muramasa and, after a fierce battle, manages to defeat him, ending the rebellion and Muramasa's control over all Zanpakutō spirits who have not already been freed.

Prelude
After many Shinigami receive Jigokuchō telling them to go to Sōkyoku Hill, 1st Division Lieutenant Chōjirō Sasakibe approaches all those gathered, but falls unconscious. When Muramasa approaches them, 7th Division Captain Sajin Komamura activates his Bankai, but is cut down by Tenken.

Members of the Gotei 13 attempt to release their Zanpakutō, but are unable to. As Muramasa reveals he has freed the Zanpakutō spirits from Shinigami control, several other Zanpakutō spirits appear and attack the Seireitei as Muramasa denounces the Shinigami.

As the Shinigami find themselves outclassed, 6th Division Captain Byakuya Kuchiki tries to subdue Muramasa. Commending him, Muramasa summons Byakuya's Zanpakutō spirit, Senbonzakura. Confronted by his own Zanpakutō spirit, Byakuya goes on the defensive and uses Shunpo to get away from Senbonzakura.

Running across the rooftops, Byakuya is engulfed by the blade petals of Senbonzakura's Bankai as he jumps. Meanwhile, after being pursued by her Zanpakutō spirit, Sode no Shirayuki, Rukia Kuchiki manages to open a Senkaimon to the Human World and falls to the ground being caught by Ichigo. Arriving, Sode no Shirayuki attacks Ichigo.

As a confused Ichigo asks Sode no Shirayuki how she is able to use Rukia's attacks, Sode no Shirayuki continues to attack Ichigo. When Ichigo gains the upper hand, Sode no Shirayuki creates a diversion to escape. After Ichigo takes her to the Urahara Shop to recover, Rukia reveals what happened in Soul Society to Ichigo and the others.

Later, when Rukia disappears, Kisuke Urahara theorizes she has likely returned to Soul Society, prompting Ichigo and Yoruichi Shihōin to go to Soul Society to help. Meanwhile, Rukia rushes through the 6th Division barracks in search of Byakuya. Confronting Sode no Shirayuki, Rukia tells her to stop attacking innocent people, but Sode no Shirayuki states she no longer takes orders from Rukia.

Initially stunned to see Sode no Shirayuki using her attacks, Rukia eventually realizes why Sode no Shirayuki left her and decides to finish the battle by binding herself to her Zanpakutō spirit and firing '''Hadō 73. Sōren Sōkatsui''' at her, trying to kill herself along with Sode no Shirayuki in order to set Sode no Shirayuki free.

In the crater left by Rukia's attack, Muramasa arrives to retrieve Sode no Shirayuki. Revealing himself to be a Zanpakutō spirit, Muramasa says he will release all Zanpakutō spirits from Shinigami control. When Ichigo proposes a change of location, they take off. Getting the better of Ichigo, Muramasa frees Zangetsu, who attacks Ichigo.

As the smoke clears, Ichigo stands with half of his Hollow mask on and chases Zangetsu to a new location. After Zangetsu attacks, the smoke clears to reveal Hollow Ichigo has taken full control of Ichigo's body. As Hollow Ichigo goes into a berserk rage, Ichigo regains control and rips his mask off. As his body returns to normal, Ichigo falls unconscious. As Ichigo awakens in his inner world, Muramasa stands before him and draws out Hollow Ichigo. Fighting Hollow Ichigo, Muramasa eventually traps him in his invisible tentacles. Freeing his inner Hollow, Ichigo returns to the real world. As Ichigo gains new resolve, Hollow Ichigo loans Ichigo his power, and Ichigo unleashes a powerful Getsuga Tenshō to finish the battle. As Muramasa grows weak and disappears, Zangetsu is freed from Muramasa's control and explains how dangerous Muramasa is.

Meanwhile, 6th Division Lieutenant Renji Abarai is confronted by Saru and Hebi, whom he does not recognize at first. When Saru and Hebi summon their Shikai, Zabimaru, Renji realizes they are his Zanpakutō spirit. Forced to find his reason to fight, Renji gains a new resolve, allowing him to release his Shikai and eventually defeat his Zanpakutō spirit by using Higa Zekkō. Elsewhere, 9th Division Lieutenant Shūhei Hisagi runs into Kazeshini, who has been cutting down everyone he encounters. Confronting Kazeshini in a forest, Hisagi resolves to kill him and states he does not care if he can no longer use his Zanpakutō. Severely wounding Hisagi, Kazeshini moves to deal the final blow, but is stopped by 3rd Division Lieutenant Izuru Kira.

Early Stages
Later, 2nd Division Lieutenant Marechiyo Ōmaeda walks with his subordinates in search of records of a Zanpakutō spirit named Muramasa ever existing. Comes across many unconscious Shinigami, Ōmaeda is confronted by a Zanpakutō spirit, whom he recognizes as Gegetsuburi. Preparing to fight Gegetsuburi, Ōmaeda is knocked out when Ichigo and 11th Division 3rd Seat Ikkaku Madarame arrive. As Ichigo defeats Gegetsuburi, Ikkaku face Hōzukimaru. After the two engage in Ikkaku's Tsuki-Tsuki Dance in order to verify Hōzukimaru's identity, Hōzukimaru activates his Bankai. Before the fight can conclude, 2nd Division Captain Suì-Fēng arrives to apprehend the Zanpakutō spirit, but Hōzukimaru escapes and Ichigo chases after him. After being stopped by a swarm of blade petals, Ichigo sees Byakuya standing on a nearby roof.

As Ichigo runs after Byakuya, he is confronted by Haineko and Tobiume, but escapes when they are confronted by their owners 5th Division Lieutenant Momo Hinamori and 10th Division Lieutenant Rangiku Matsumoto. Initially taking on their own Zanpakutō spirits, Momo and Rangiku struggle to defeat them, but manage to trick the Zanpakutō spirits by switching opponents and defeating them with Kidō before tying them up and celebrating. Elsewhere, 10th Division Captain Tōshirō Hitsugaya confronts his Zanpakutō spirit, Hyōrinmaru, who has lost his memories.

Hitsugaya tries to get Hyōrinmaru to remember who he is, but does not succeed. Managing to release his Shikai, Hitsugaya uses Ryūsenka. encasing both himself and Hyōrinmaru in ice. Inside the ice, Hitsugaya calls out Hyōrinmaru's name, causing Hyōrinmaru to remember who he is. Shattering the ice, Hyōrinmaru carries Hitsugaya out. Elsewhere, Ichigo runs into Momo and Rangiku, who are having Haineko and Tobiume taken away. When Muramasa stumbles out of a Garganta, Ichigo attempts to fight him, only to be confronted by Senbonzakura.

After Senbonzakura activates his Bankai, Ichigo realizes he is Byakuya's Zanpakutō spirit. As the two fight, Ichigo manages to gain the upper hand before Byakuya appears. Preventing Senbonzakura from attacking Ichigo, Byakuya fires '''Hadō #33. Sōkatsui''' at Ichigo. As Byakuya tells Ichigo to prepare to die if he tries to impede Muramasa's plans, he, Senbonzakura, and Muramasa disappear behind a swarm of blade petals. The next day, the news of Byakuya's betrayal spreads through the Gotei 13, shocking many and upsetting Rukia.

At the cave of the Zanpakutō spirits, Byakuya enters, much to the surprise of the Zanpakutō spirits. When asked why he is there, Byakuya says he is doing as his pride dictates. When Senbonzakura states Byakuya must kill Sode no Shirayuki, his sister's Zanpakutō spirit, in order to prove his loyalty, the Zanpakutō spirits initially believe they have him trapped, but Byakuya attacks Sode no Shirayuki. Though Sode no Shirayuki puts up a minor fight, Byakuya makes quick work of her by binding her with '''Bakudō #63. Rikujōkōrō''' and cutting her down, causing her to revert to her sword form. Afterwards, Muramasa tells Byakuya he has a job for him.

Late at night, Rukia awakens in Byakuya's office to find many unconscious Shinigami on the ground. As Byakuya stands before her, Senbonzakura tosses the broken Sode no Shirayuki to her. As Byakuya tells her to stay away, Rukia asks him what he means as Senbonzakura prepares to attack her. Appear, Renji attacks Byakuya and tries to use Shikai, but Byakuya points out he should not be able to. When Saru and Hebi appear, Senbonzakura stops their attack. As Renji and Byakuya relocate to the roof to continue their battle, Saru and Hebi fight Senbonzakura in the building. Though Renji, Saru, and Hebi initially overwhelm their opponents, Byakuya and Senbonzakura gain the advantage and defeat them. As several other Zanpakutō spirits arrive, dozens of Keigun arrive alongside several other Shinigami and Ichigo.

11th Division 5th Seat Yumichika Ayasegawa confronts his Zanpakutō spirit, Ruri'iro Kujaku. After seemingly being beaten and drained by his Shikai ability, Yumichika defeats Ruri'iro Kujaku and returns him to his sword form. Elsewhere, Ikkaku faces Hōzukimaru once more. Hōzukimaru activates his Bankai, but Ikkaku reminds him of his strength and position, and the two charge at each other. Afterwards, a defeated Hōzukimaru collapses alongside an injured Ikkaku. On the rooftops, Suì-Fēng encounters Tenken and Gonryōmaru. Though the two put up a fight, Suì-Fēng activates Shunkō and knocks Gonryōmaru back before catching Tenken's blade.

Meanwhile, 4th Division Lieutenant Isane Kotetsu and 7th Division Lieutenant Tetsuzaemon Iba encounter Ashisogi Jizō. Along with Rangiku and Momo, they run from its deadly poison and blades before being incapacitated by it when it activates its Bankai. Elsewhere, Izuru battles Kazeshini and eventually knocks him out with an explosive armband and Kidō. Though Wabisuke incapacitates him, Izuru is saved by the arrival of 11th Division Captain Kenpachi Zaraki. Back at the barracks, Ichigo fights Senbonzakura. The two put up a fierce fight, with neither injuring the other, but as Ichigo goes to attack Senbonzakura after a decisive hit, he finds his opponent is not there, and is engulfed by the poison of Konjiki Ashisogi Jizō, causing him to collapse.

While holding back Tenken's attack, Suì-Fēng finds a Hōmonka on her back. When Suì-Fēng doubts the spirit before her is Suzumebachi, Suzumebachi offers to sting Suì-Fēng again in the same spot and see what happens. When Zaraki arrives, Suì-Fēng berates him for coming so late. When Zaraki unleashes a surge of Reiatsu, Suì-Fēng and Suzumebachi are sent flying away. Continuing from where they left off, Suzumebachi taunts Suì-Fēng and attacks her. Activating Shunkō to stop the attack, Suì-Fēng cuts off Suzumebachi's stinger, ending the fight. When Suì-Fēng collapses from exhaustion, Yoruichi arrives to catch her and informs Suì-Fēng she has discovered the location of Captain-Commander Genryūsai Shigekuni Yamamoto.

Meanwhile, Zaraki encounters Byakuya. Stating he has always wanted to fight Byakuya, Zaraki attacks him. The two continue to clash, with Byakuya using Shunpo to escape Zaraki's powerful attacks. After seeing Zaraki's fierce determination, Byakuya finally decides to take their fight seriously, but the ground around them rumbles as Konjiki Ashisogi Jizō reappears and Byakuya leaves. Grabbing Ashisogi Jizō, Zaraki yells at it for interrupting his fight, but Mayuri appears and detonates Ashisogi Jizō, returning it to its sealed state.

Middle Stages
After the confrontation with the Zanpakutō spirits, 4th Division Captain Retsu Unohana appears and begins healing the wounded. When Zaraki prepares to search for Byakuya, Yoruichi tells him to wait before revealing she knows where Byakuya and Yamamoto are. In the cave of the Zanpakutō spirits, Muramasa shows Byakuya where Yamamoto is as Byakuya sees Yamamoto under a pyramid-like barrier with three Zanpakutō spirits floating above it. Back in the Seireitei, Yoruichi puts together a search team of 8th Division Captain Shunsui Kyōraku, 13th Division Captain Jūshirō Ukitake, and Ichigo, with 11th Division Lieutenant Yachiru Kusajishi persuading Zaraki to go as well. They head to the cave, where Zaraki promptly goes off on his own into the cave with Yachiru cheering him on. As Yoruichi tells everyone to be cautious, they enter the cave themselves.

Inside the cave, Yoruichi and Ichigo head inwards before being attacked by Haineko and Tobiume. As Yoruichi takes them on, Ichigo moves forward. Haineko and Tobiume team up against Yoruichi, who overwhelms them with her incredible speed. After being trapped by rocks, Yoruichi deduces Haineko and Tobiume are stalling for time. Getting up, Yoruichi binds Haineko and Tobiume to a wall with '''Bakudō #30. Shitotsu Sansen'''. Realizing what Muramasa is after, Yoruichi heads further inside. Elsewhere, Shunsui and Ukitake run into Katen Kyōkotsu and Sōgyo no Kotowari. Heading off in different directions with their Zanpakutō spirits, Shunsui and Ukitake handle them without difficulty.

After regrouping, they realize the Zanpakutō spirits were stalling instead of trying to harm them. Evading Katen Kyōkotsu and Sōgyo no Kotowari, Shunsui and Ukitake continue further into the cave and realize Muramasa is after Ichigo's ultimate attack. After getting lost, Zaraki and Yachiru enter a den, where they are confronted by Tenken and Gonryōmaru. After defeating Gonryōmaru and realizing they are not using their full power, Zaraki fights Tenken. After catching the giant's sword with his hand, Zaraki taunts Tenken, who activates his Bankai, breaking through the roof and becoming Kokujō Tengen Myō'ō. Becoming excited, Zaraki attacks him.

After being separated from Yoruichi, Ichigo encounters and chases Minazuki, who repeatedly dodges his attacks. Encountering Kazeshini, Ichigo defeats him with a Getsuga Tenshō and moves to the top of the cave, where he discovers Yamamoto's barrier. Upon encountering Muramasa, Ichigo engages him in battle. When Muramasa tells him to use his ultimate attack, Ichigo dons his Hollow mask and fires a Getsuga Tenshō at him. As Yoruichi, Shunsui, and Ukitake arrive, Muramasa redirects the Getsuga Tenshō, which destroys the barrier surrounding Yamamoto. As Ichigo is informed of what he has done, Yamamoto declares the Shinigami have lost this round as Ryūjin Jakka manifests and destroys the cave.

Revealing he placed himself within the barrier to prevent Muramasa from gaining access to Ryūjin Jakka, Yamamoto informs everyone of who Muramasa is and who Muramasa's master, Kōga Kuchiki, was before revealing Kōga had led a revolt and Muramasa did not kill him, but was after the method to free him, which only Yamamoto knew of. Surrounded by flames and needing to escape to stop Muramasa, Ichigo tries to break out, but is stopped. Arriving, Hitsugaya and Hyōrinmaru freeze Ryūjin Jakka's flames long enough for Ichigo to escape.

Later Stages
Arriving in the Human World, Muramasa coughs up blood and collapses. When he awakens, he finds Orihime Inoue healing him. When Uryū Ishida and Yasutora Sado arrive to stop him, Muramasa dodges their attacks. After Senbonzakura arrives to aid Muramasa, Rukia arrives to stop Muramasa. Soon, Muramasa reveals his true purpose and unleashes many large Hollows. As Uryū, Sado, and Rukia fight the Hollows, Muramasa accomplishes his goal and releases Kōga from his prison as Ichigo arrives.

Now released, Kōga shocks everyone by stabbing Muramasa in the stomach. As Kōga prepares to kill Muramasa, Byakuya appears and blocks his attack. Revealing he and Byakuya have teamed up since the beginning in order to stop Muramasa and prevent Kōga from being released, Senbonzakura returns to his sword. Attacking Kōga, Byakuya soon finds himself caught by Kōga's illusion powers. After Kōga traps Byakuya, Senbonzakura activates his Shikai and saves Byakuya, shocking Kōga. Using Senkei, Byakuya activating Shūkei: Hakuteiken and charges at Kōga. Afterwards, as Senbonzakura catches Byakuya, Kōga falls into the lake and dies.

Having been abandoned by his master, Muramasa loses control of the multiple Hollows whom he had been storing inside of him and unleashes countless Gillians into the area. As everyone unites to defeat them, Muramasa loses control and takes on a Hollow-like form. Though Ichigo manages to slightly overpower him with his mask, the many Gillians make the fight tougher. Soon, Muramasa loses control of his Reiatsu and is enveloped by a large dome-like structure. As a Garganta opens in the sky above and unleashes hundreds of Gillians, the Zanpakutō spirits, recently freed from Muramasa's control, arrive to team up with the Shinigami and force the Garganta to close.

Having been enveloped in Muramasa's Reiatsu, Ichigo finds himself in Kōga's inner world, where he finds Muramasa in his normal state. Manifesting his sword, Muramasa attacks Ichigo. When Muramasa traps Ichigo with his tentacles, a pillar falls, disrupting the attack and allowing Ichigo to completely sever the threads with a Getsuga Tenshō. As Muramasa uses more illusions to fight him, Ichigo connects with Zangetsu and sends Muramasa flying through several pillars. As Ichigo criticizes his beliefs, Muramasa refuses to give up as his Hollow mask begins to form on his face. Ripping it off, Muramasa charges at Ichigo for a final time and is defeated.

Aftermath
As the dome fades away, a defeated Muramasa falls. As the Shinigami and their Zanpakutō spirits defeat the Gillians, Ichigo comforts Muramasa, who dies while revealing what he hopes will happen some day and fades away as his sword snaps in two. As Ichigo confirms everyone is okay, the Zanpakutō spirits return to their swords. When Byakuya thanks Ichigo, Ichigo accepts his thanks before leaving. However, with many Shinigami dying during the attacks, many Tōjū are created.