Byakuya Kuchiki vs. Kōga Kuchiki

 is a fight that takes lace during the Zanpakutō Rebellion in which Byakuya Kuchiki reveals his true motives behind his apparent betrayal and defends the honor of the Kuchiki Clan.

Prologue
After being freed from his seal by his Zanpakutō spirit, Kōga Kuchiki breaks his sword and calls Muramasa nothing but a tool. He berates him for not coming when he called him all those years ago when he was being sealed. Muramasa explains that he did not hear Kōga and wanted nothing more than to lend his powers to him. Kōga refuses to listen to Muramasa's pleas, preparing to finish the injured Muramasa off but is stopped by Byakuya Kuchiki, who says that he cannot believe he called his sword nothing more than a tool. Kōga scowls and Byakuya says that Kōga does not deserve the title of Shinigami.

The two back away from each other and Kōga notices Byakuya's scarf and Kenseikan. He realizes that Byakuya must be from the Kuchiki Clan and Byakuya says he is the 28th head of the clan. Noting the 28th, Kōga says it has been a long time since he was sealed. He asks if Ginrei Kuchiki is still alive, but Byakuya says it would be best if Kōga did not speak his name because after tarnishing his family's honour, he has no right to speak of it. Ichigo Kurosaki and Rukia Kuchiki wonder what is going on but Senbonzakura tells them to just watch and that it is a battle for the Kuchiki family honor. Ichigo wonders what is going on as Senbonzakura was under Muramasa's control. Senbonzakura says that he was but when he and Byakuya first clashed, Byakuya fired a Kidō spell across his face, freeing him from Muramasa's control. Senbonzakura says that Ginrei had told Byakuya of Kōga's rebellion, informing him that it is the sole duty of the Head of the Kuchiki Clan to kill him, should he be released from Yamamoto's seal. Byakuya had infiltrated the library in order to find records on Kōga but it was left out of the records. Rukia says she cannot believe that Kōga was once a member of the Kuchiki Clan. Ichigo yells that they should have told everyone but Senbonzakura says it was all for the sake of finding where Kōga was sealed and thus he pretended to still be under Muramasa's control but when he could not get Kōga's location, Byakuya had to get close no matter how it appeared. Ichigo asks why they went so far and Senbonzakura says that it is simply Byakuya's duty.

Kōga asks if Byakuya plans to seal him again but Byakuya says that Kōga must die here for tainting the family name. Kōga says that Byakuya is arrogant enough to be a Kuchiki, stating that if Byakuya really is the head of the Kuchiki clan then is more than enough reason to fight him. Muramasa offers his abilities to Kōga, but he simply picks up his sword, slicing it in half. This shocks everyone, causing Muramasa to fall onto the ground in anguish. Kōga says that Muramasa will only get in his way and that he has no need for a weak katana. Ichigo yells at Kōga asking if he even knows what a Zanpakutō is. Kōga repeats that a Zanpakutō is merely a tool and he can always replace it. Muramasa then loses control and his surge in Reiatsu causes a group of Gillian to appear. Byakuya calls him foolish and goes to defeat the Gillian but Ichigo gets there first. He tells Byakuya to leave the Gillian to them and to go teach Kōga a lesson.

Battle
Byakuya calls Senbonzakura and the two dive down as Senbonzakura reforms into a katana in Byakuya's hand. Kōga quickly grabs one of the spears he was sealed with and meets Byakuya in mid air. They break and Byakuya asks what Kōga is doing. Kōga responds that he told Byakuya he had no need for any particular weapon, hence why he is using the spear. They attack each other again, each making and blocking a series of strikes from the other. Byakuya comes very close to cutting Kōga's face but Kōga dodges at the last second. Kōga attacks again and hooks Byakuya's sword in his spear while swinging the sharp end point around to Byakuya, who narrowly dodges.

Kōga compliments Byakuya's skill, saying he would expect as much from the head of the house. He jumps away and asks Byakuya if his kidō is as good, firing a Kongōbaku blast at Byakuya who negates it with his own Sōkatsui. Kōga continues, firing a Gaki Rekkō spell which Byakuya easily evades, countering with his own barrage of Byakurai. Kōga appears behind Byakuya and fires a Hyōga Seiran spell, spewing ice from the tip of his spear. Byakuya places a Dankū spell to take the force of the attack, but the spell surges around the barrier, wiping out many of the Gillian in the area. Before long, the barrier cracks into pieces, forcing Byakuya to move away, allowing the spell to freeze the lake behind him.

Kōga smiles as he looks ahead of him at the ice pillar his attack left. Suddenly, Byakuya bursts through the ice by releasing his Zanpakutō. Byakuya says that Kōga's Kidō is nothing compared to his Senbonzakura. Kōga tells Byakuya to not be so cocky, swiftly attacking Byakuya who leaps into the sky. As Byakuya is airborne, Kōga unleashes an unseen attack that stops him in mid-air. Looking into the reflection of the lake, Byakuya sees many threads binding him. Kōga says that he has Byakuya and that he cannot move an inch. Byakuya unleashes his Zanpakutō again, severing the threads constricting him. He then sends his Senbonzakura's petals to attack Kōga, who spins his blade in defense. Kōga stops the attack but his spear shatters in the process. Byakuya quickly appears behind Kōga, saying it is over and cuts Kōga in half. As he looks through the two halves of Kōga's body, he sees the real Kōga standing in front of the illusion, shocking him. Kōga intercepts his movements, telling Byakuya that he is wide open, slashing across his back.

Byakuya swiftly turns around and cuts Kōga in half again but he then appears in the air above and slashes down, cutting Byakuya and revealing he is actually right on top of the captain. Byakuya asks what is going on and Kōga says that Muramasa may have been able to control Zanpakutō but it was born from his own ability to send out his own Reiatsu and distort his opponent's five senses. Kōga appears at Byakuya's side and Byakuya dispels the illusion, but Kōga once more appears in front of Byakuya saying he has total control over his senses. He says that Byakuya cannot see him clearly even though he is right in front of him. Byakuya asks if it is an illusion but Kōga says that it is much more than that. He then tosses the end of his spear at Byakuya and it phases right through him as another one comes at him and actually hits him this time. Kōga says that Byakuya's depth perception does not match his katana's reach, rendering him useless in the fight. Kōga then creates many clones as he continues to speak. He taunts Byakuya, stating that his ability would not have worked had Byakuya sealed off his heart like Ginrei and Yamamoto had. He says that Byakuya let his guard down when he broke Muramasa, but Byakuya states that that isn't the case. He continues, explaining that he faced Kōga with an open heart in order to kill him. Kōga says he has guts for talking to him like that.

Byakuya goes to attack with his Zanpakutō but Kōga grabs another spear and throws it at Byakuya, whilst distorting Byakuya's vision and making him see a multitude of spears flashing in front of him. A spear wraps around Byakuya's arm, knocking his sword away. Kōga grabs two more spears and tosses one at Byakuya, wrapping around his other arm. Kōga unleashes another Hyōga Seiran and Byakuya counters with Dankū but the Kōga Byakuya saw was just an illusion and the spell hits him from behind, freezing him in a chunk of ice. Kōga calls Byakuya pathetic and says he is powerless without his Zanpakutō. He claims that it does not matter who he fights as all will bow down to him and that even without his Zanpakutō, he is the strongest. He then says that they will finish their fight. Kōga charges at Byakuya, attempting to finish him off. However, he is suddenly stopped by Senbonzakura who reforms into his spirit form, informing Byakuya that if he has lost his senses then he shall become his eyes and fight for him. Senbonzakura breaks the ice and reforms once more into a katana.

Kōga, angered, says he will just have to distort the sword's senses as well. Byakuya says that he will not allow that to happen, initiating his Bankai. He activates Senkei, telling Kōga that this is his Bankai's true form and that it focuses all its power on offense to defeat a single opponent. He says that it does not matter if Kōga distorts his perception as his blades will hit regardless. Kōga charges at Byakuya and he follows. As they hit each other, they unleash a huge amount of power before breaking off. They clash once more before breaking off again, as Kōga then uses his technique once more to tie Byakuya up with invisible threads. Senbonzakura appears once more though and snaps the threads, allowing Byakuya to charge at Kōga giving him less than a second to dodge, gradually wearing him down.

Kōga asks where Byakuya's newfound power is emanating from and Senbonzakura answers that both he and Byakuya are fighting him. He says that Shinigami and Zanpakutō are meant to be in a state of symbiosis and can only reach their true potential when their souls resonate in perfect harmony. He claims Kōga only cares about his own vanity and could never hope to defeat them. Kōga silences them, stating that they are the ones who do not get it. He says that no one acknowledges his deeds, claiming he was ignored and branded as a traitor so he created a place for himself alone. He then says that only those with power will rule and that he shall be the king of the new world. However, Byakuya calls him foolish and says he has not grasped the meaning of true power. He says the power Kōga needed was that of communication with others as he does with his Zanpakutō. Kōga claims the power of communication is meaningless and that his power is godly. Byakuya says that he then does not have anything more to say and tells Kōga to blame his immaturity for keeping him from realizing his own arrogance. He raises his sword to Kōga and says that he will perform his duty as the head of the Kuchiki clan. He activates his Shūkei: Hakuteiken technique and Kōga calls it impressive, saying there has not been a house head as strong as Byakuya. Byakuya claims that the technique is his final act of respect towards Kōga as a former member of the Kuchiki clan. Kōga glares at Byakuya and says he will defeat him, finally expunging his ties from the prison known as the Kuchiki clan. The two then charge at each other one last time.

Aftermath
After they collide, the lake that was formerly turned to ice returns to just water from the impact. Byakuya stumbles onto the ground, but Senbonzakura catches him. Kōga bleeds out and falls, saying it is impossible as he does so. He catches himself by stabbing his spear into the ground, stating that it isn't over. He calls to Muramasa, who is engulfed in his reiatsu, and as such gets no response and wonders what is wrong. He calls to his Zanpakutō one final time before plunging into the icy water below, dead. Byakuya says he is alright and Senbonzakura says that if Kōga wasn't so strong, Byakuya's attack would have swallowed him whole. Byakuya says it is only natural for someone with such great power to possess a weak heart. Senbonzakura says he is the polar opposite of Byakuya. who risked his name by becoming a traitor in order to fight for his beliefs. He then says that Byakuya can finally return to where he belongs and Byakuya says that he is very talkative. Having emerged victorious in his fight with Kōga, Byakuya goes to aid the others in defeating Muramasa and the Gillian.