Beast Swords arc

The Beast Swords arc is an anime-exclusive mini-arc focusing on the Tōjū, Zanpakutō spirits that were materialized by Muramasa, but were not saved by their Shinigami, causing them to go into a blind rampage.

The Tōjū Appear
A party is being held at Byakuya Kuchiki's mansion for the Sixth Division. Renji Abarai thinks this is a good time for the division members to fraternize with their captain, while Rukia Kuchiki notices how nervous everyone looks. Renji is surprised that Byakuya is hosting the party in his own home, while Rukia says he should be grateful Byakuya's looking after his men. Renji is whisked off by one of his underlings while Rukia is lecturing him. Annoyed, she returns to her quarters, when she hears a scream. She investigates, and discovers two interlopers smashing up one of the rooms. She moves to engage them, but remembers she doesn't have her Zanpakutō. She narrowly avoids their attacks, until Sode no Shirayuki arrives. She drives off one of them, but is ambushed when she tries to prevent him from escaping. She is saved by Senbonzakura. Rukia is shocked to see them in spirit form again and they tell her they never agreed to just be swords. Their argument is cut short by Byakuya's arrival, and one of the interlopers body combusts, revealing a Zanpakutō.

Rukia, Byakuya, and their Zanpakutō spirits go over to Mayuri Kurotsuchi's place to ask him why there are still some Zanpakutō spirits around. He reveals that he never intended to return the spirits to Zanpakutō form. He continues to explain that the Zanpakutō that they encountered before were Zanpakutō spirits that were freed from Muramasa but they succeeded in killing their masters. While this would normally kill the Zanpakutō too, these are abnormal. Mayuri identifies this as something new; he names the new phenomenon Tōjū and tasks Rukia with capturing the one that escaped earlier. Mayuri warns them that the Tōjū have full access to their abilities and are effectively in constant Bankai.

Rukia ponders the difficulty of the task, but Senbonzakura and Sode no Shirayuki are both keen to fight. Renji arrives to inform them of a change of guard. Byakuya leaves Rukia in charge while he deals with this. Senbonzakura and Sode no Shirayuki both suggest large scale destruction to lure out the target but Rukia quickly discounts this. Sode no Shirayuki suggests that they have another party, this time at Tenth Division's headquarters.

Toshiro Hitsugaya is not happy with this, but allows it anyway since everyone needs a well deserved break from the battle with Muramasa. The plan fails however, as there is no sign of the target.

Rukia and Sode no Shirayuki have a quiet chat afterwards. Sode no Shirayuki reveals her inner turmoil regarding the events revolving around Muramasa. Rukia tries to remind her of the times when it was her who needed saving. This is cut short however when one of the Tōjū from earlier arrives. Capturing him proves more difficult when he assumes a tornado-like form but they are able to defeat him with a combination of her Shikai abilities and Kidō.

Rukia reports to Shunsui Kyōraku and Jushiro Ukitake that the Tōjū were delivered to the Shinigami Research and Development Institute and Ukitake reveals that similar reports are coming in from elsewhere.

Tōjū In The Human World
Before long the Tōjū begin to slip into the Human World. The first to cross over appears to be in a bad shape, due to the separation from his master. He enters the Human World next to a large construction sight in Karakura Town and soon runs into Substitute Shinigami Ichigo Kurosaki. The latter is puzzled by this strange new being and defends himself when the Tōjū attacks. Tōshirō Hitsugaya, who followed the Tōjū, attempts to cut him down but the Tōjū, though injured, makes a getaway.

Hitsugaya is briefing Ichigo and Kisuke Urahara about the goings on in Soul Society and of the existence of the Tōjū, when they hear the ruckus of a heated argument from the hallway. Rangiku Matsumoto and her Zanpakutō, Haineko have come to the Human world after their captain and despite his orders. Haineko quickly invokes the envy and rivalry of Ririn, who is nonetheless powerless to do any real damage to the Zanpakutō spirit. Rangiku and Haineko have been busy taking sexy photographs of themselves, which garner much interest from most of the male population of the Urahara Shop. Hitsugaya quickly loses his patience for his two underlings.

Back at Seireitei, Kyōraku and Ukitake are busy entertaining their Zanpakutō spirits. They agree between them that while they don't mind the Zanpakutō spirits being out, the Tōjū have nowhere to go. Besides, they decide, it's much more natural for the spirits to be inside the swords. Hearing this, Katen Kyōkotsu and Sōgyo no Kotowari punish their "masters". Sode no Shirayuki tells Rukia just how effective Captain Kurotsuchi was in bringing the Zanpakutō spirits out of Muramasa's hypnosis.

It is explained that when a Shinigami calls out his Zanpakutō's name, they resonate with each other and are able to fight as one. Muramasa's brainwashing destabilized the resonance and stimulation in the affected spirits, and Kurotsuchi discovered a way to re-stabilize them. Ukitake and Kyōraku, wanting to push Kurotsuchi to further research into the Tōjū problem, send Nanao Ise to him with a box of cakes. The captain accepts the cakes, but takes his time starting the research because the subject doesn't peek his curiosity.

Over in Karakura, the lost Tōjū is in trouble; a large Hollow spots and attacks him. The Tōjū tries to run away, but the Hollow catches up to him and devours him. Hitsugaya and Hyōrinmaru sense his presence for a moment but lose it the next, and Hitsugaya prefers not to call Matsumoto and Haineko, saying they would only make things worse.

In her house, Orihime Inoue finds Haineko too cute for words, in a Karakura High School girl's uniform. The three go on a girls night out but Rangiku uses it to track the Tōjū. She senses his presence in a skyscraper still under construction, but notes that it has somehow changed. They head out for the tower at about the same time as Ichigo, who is patrolling nearby.

As Rangiku arrives at the tower she realizes the Reiatsu can't be that of a Tōjū. Haineko spots a strange creature, standing above them on top of several steel beams suspended from a crane. The creature is an upright standing Hollow holding a spear like weapon in his hand. Before Rangiku can ingest her Soul Candy, the Tōjū cuts the straps holding the beams, and Haineko grabs her and pulls her to safety, causing Rangiku to drop the Soul Candy. Orihime uses Santen Kesshun to protect them from the falling beams. Haineko volunteers to deal with the strange Hollow but before she can react the creature attacks and pins her to a wall, demanding she returns his master to him. Just as the Hollow is about to strike, Ichigo arrives and cuts his arm, freeing Haineko.

The Hollow runs away and Ichigo follows and manages to cut him off on the arm of the crane. Zangetsu tells Ichigo that the Hollow is in fact the Zanpakutō from before, who has been absorbed by a Hollow and fused with it. When the creature attacks again, Ichigo knocks his weapon away and intends to use Getsuga Tenshō, but the creature launches a powerful Cero that Ichigo can barely block. Hitsugaya himself arrives to finish the job by releasing Hyōrinmaru and freezing the creature. The Tōjū's weapon breaks, noting that the tortured spirit is now dead. Hitsugaya warns Ichigo and the others that the Tōjū will prove to be a most troublesome foe.

Sometime later, Renji and Zabimaru arrive in the Human World to deal with the Toju. They stumble upon one, but Zabimaru's snake half goofs off and the Toju escapes. When the snake finds the Toju again, the latter tricks the snake into going off on his own so that the Toju can kill the two Zabimaru separately. The Toju once again escapes just as Renji and Zabimaru's baboon half catch up. The baboon scolds the snake which causes him to run away. Overjoyed to finally be by himself, the snake Zabimaru goes around Karakura trying to buy food, but canot obtain anything because most of the town's humans are not spiritually aware. When the snake stops at a conveiniece store, Karin and Yuzu Kurosaki find him and brings him to their home. Ichigo finds the snake and concludes that Renji is in the Human World. That night, the snake goes out to confront the Toju from earlier. Despite his determination, Zabimaru finds himself outclassed and is almost killed by the Toju. Renji and Zabimaru's baboon half arrives and finishes the Toju. The snake half gives a silent goodbye to Karin and askes Ichigo not to tell his sister that he left. With that, Both Zabimaru and Renji return to Soul Society.