Ryoka Invasion

The Ryoka Invasion was a major conflict marking the first time Ryoka had ever gained ground against the elites of the Soul Society. It was an invasion by Ichigo Kurosaki, Uryū Ishida, Yasutora Sado, Orihime Inoue and Yoruichi Shihōin into Soul Society to save their friend Rukia Kuchiki from being executed.

The Invasion began when Ichigo and his friends decided to save Rukia from an unjust fate that Ichigo believed was more his fault than hers. They proceeded to infiltrate the Soul Society itself, immediately causing a stir that created a level of distrust among the Gotei 13, fracturing it with the seemingly impossible death of one of their own, Captain Sōsuke Aizen, which was blamed on the Ryoka invaders.

The Invasion ended with the defeats of various captains and lieutenants at the hands of Ichigo and his friends, but the situation quickly became even more complicated when the entire Gotei 13 was revealed to have been the victim of an elaborate conspiracy. Sōsuke Aizen was not only revealed to be alive, but the mastermind behind the whole conspiracy, with Captains Gin Ichimaru and Kaname Tōsen acting as his subordinates. Aizen's goal was the retrieval of the Hōgyoku, a creation of Kisuke Urahara, that had been hidden in Rukia's body. Now in hand, he escaped, leaving the Gotei 13 to ponder their next move.

Prelude
After finishing his training, Ichigo reunites with Orihime, Uryū, Chad, and Yoruichi. They prepare to go to Soul Society to save Rukia.

Side Tracked
Ichigo and his friends arrive at Soul Society. They have to defeat a gatekeeper named Jidanbō Ikkanzaka to enter Seireitei, the walled city in which the Shinigami reside. Ichigo easily defeats Jidanbō, who opens the gate, allowing them to enter Seireitei. However, when they attempt to pass through, the 3rd Division captain, Gin Ichimaru, attacks them and closes the gate, injuring Jidanbō. While searching for another way to enter, Ichigo encounters Ganju Shiba, whose hatred of the Shinigami causes him to fight Ichigo. The fight ends prematurely, as Ganju leaves for unknown reasons. Later, Yoruichi asks an old friend named Kūkaku Shiba, who also happens to be Ganju's sister, to help them with entering Seireitei. After much consideration, she agrees to help them out. To use Kūkaku's cannon to enter Seireitei, Ichigo and his friends must first learn to focus their spiritual energies. Meanwhile, behind the walls of the city, an emergency meeting is called for all the Gotei 13 captains to interrogate Gin about why he allowed the invaders to survive. However, a sounding alarm interrupts the meeting. Before leaving, 5th Division captain, Sōsuke Aizen, confronts Gin in front of the 10th Division captain, Tōshirō Hitsugaya. He rebukes his flimsy excuse for allowing the invaders to escape.

Intruders
After Ichigo's group completes their training, Ganju decides to join them because his older brother was killed by a Shinigami. He comes to the realization that Ichigo is not an evil person, and wants to confirm if Shinigami are evil or not. They enter Seireitei through a cannon shot, but are separated during their descent into the city. Ichigo and Ganju encounter and fight two 11th Division members, Ikkaku Madarame and Yumichika Ayasegawa. Ichigo successfully uses his Zanpakutō to defeat Ikkaku.

Ganju defeats Yumichika by exploding fireworks in his face. He later reunites with Ichigo. Meanwhile, Uryū and Orihime are confronted by Jirōbō Ikkanzaka, the 4th Seat of the 7th Division, whom Uryū easily defeats.

Rematch: Ichigo vs. Renji
Ichigo and Ganju are confronted by a large group of Shinigami, and escape by using a clumsy 4th Division officer, 7th Seat Hanatarō Yamada, as a distraction. Hanatarō informs them of a shortcut to the place where Rukia is being held. While going to find Rukia, Renji Abarai, the lieutenant of the 6th Division, confronts Ichigo. Ichigo overpowers Renji by using all his spiritual powers that he learned with Urahara. Before falling to the ground, Renji recalls his long-time friendship with Rukia and asks Ichigo to save her.

Middle Stages
Captain Byakuya Kuchiki wants to have Renji executed for being defeated by Ichigo, but is talked out of it. Captain Hitsugaya suspects that something is wrong with Gin and tells his friend Momo Hinamori, the 5th Division lieutenant, to be careful around him. The following day, Captain Aizen is found dead. Thinking Gin might be responsible, Hinamori attempts to attack him, but instead attacks Gin's lieutenant, Izuru Kira. Both of are jailed for fighting. Hanatarō heals Ichigo, and they, along with Ganju, continue the rescue mission. They are attacked by the 11th Division captain, Kenpachi Zaraki. Ichigo stays to fight against him while Hanatarō and Ganju continue on towards Rukia. Meanwhile, Chad is confronted by the 8th Division captain, Shunsui Kyōraku, who easily defeats Chad. Kyōraku decides only to arrest Chad instead of killing him, as he realizes that he is not a bad person. In his fight against Kenpachi, Ichigo is initially easily defeated. Zangetsu appears to test him. Ichigo fights against his Hollow side to determine whom will be worthy of Zangetsu. As Ichigo realizes that he knows nothing about Zangetsu, the fight is stopped and Ichigo returns to fight Kenpachi again. This time, he is able to use all the power from Zangetsu, and as a result Ichigo is able to successfully battle Kenpachi to a draw. Kenpachi's lieutenant, Yachiru Kusajishi, takes him to another place and Kenpachi confesses that he lost because he has never been able to truly know his Zanpakutō. Ganju and Hanatarō find Rukia, but Ganju attempts to kill her as he realizes that she is the Shinigami responsible for his brother's death.

Byakuya goes to the prison to kill Ganju and Hanatarō. Unwilling to allow Hanatarō to fight, Ganju faces Byakuya, and is almost killed. As Ichigo awakens after his fight against Kenpachi, he discovers that Yoruichi was really a woman who took the form of a cat. They encounter Byakuya; Ichigo fights him, but is knocked out by Yoruichi Shihōin, who Byakuya recognizes her as the former Commander-in-Chief of the Onmitsukidō. Together they escape from the prison. She intends to train Ichigo so that he will be able to use his Bankai, a state in which the Zanpakutō becomes considerably more powerful. Uryū and Orihime continue towards Rukia's location and are attacked by Mayuri Kurotsuchi, the 12th Division captain. Mayuri sacrifices his soldiers in order to kill Uryū, but fails. Mayuri reveals that he has experimented on many other Quincy, including Uryū's grandfather, Sōken Ishida, and was responsible for his death.

Uryū uses the Quincy's rare techniques to overcome the injuries that Mayuri inflicted upon him. In this state Uryū overpowers Mayuri, but Mayuri escapes by transforming into a liquid mass. Uryū goes toward Rukia's location, but in transit is attacked by the 9th Division captain, Kaname Tōsen. Ichigo continues his Bankai training by repeatedly battling Zangetsu. Orihime, Uryū, Ganju, and Chad are freed by Kenpachi, who wants them to guide him to Ichigo. After reading the last correspondence from Aizen, Hinamori escapes from prison and goes to where Hitsugaya and Gin are preparing to fight. She points her Zanpakutō at Hitsugaya and accuses him of killing Aizen. Hinamori desperately attacks Hitsugaya, who knocks her out. Hitsugaya furiously attacks Gin, but as Gin attacks an unconscious Hinamori, Hitsugaya's lieutenant, Rangiku Matsumoto, tells Gin to leave. The 13th Division captain, Jūshirō Ukitake, discovers that Rukia's execution was unexpectedly moved to the following day and prepares to save Rukia. Rukia reminisces about the time she spent in the 13th Division with its lieutenant and Ganju's brother, Kaien Shiba. The times were good until a Hollow took possession of him and Rukia was forced to kill him in Hollow form.

End Stages
Kenpachi, Ikkaku and Yumichika confront the 7th and 9th Division captains and lieutenants because Kenpachi is helping the intruders. Renji attempts to rescue Rukia, but is confronted by his captain, Byakuya Kuchiki. Renji unleashes his Bankai. With his Bankai, Renji surpasses Byakuya until Byakuya releases his own Bankai. In doing so he almost kills Renji. Renji still attempts to fight, but is only able to inflict a minor injury on Byakuya. Meanwhile, Kenpachi overpowers Kaname Tōsen and the 7th Division captain, Sajin Komamura, forcing Tōsen to unleash his Bankai. In this state, Tōsen creates a space in which Kenpachi cannot see his surroundings. In the end, Kenpachi allows Tōsen to attack him so that he can get in close contact with him and ultimately defeat him. Tōsen is saved by Komamura, who starts to fight Kenpachi. Rukia's execution ceremony begins. However, as the execution is proceeding, Ichigo comes to her rescue. The captains Ukitake and Kyōraku destroy the Sōkyoku, which is the large Zanpakutō used for executions, and Ichigo throws Rukia to Renji so that they can escape the scene. Ichigo then starts fighting against Byakuya. Ukitake and Kyōraku are attacked by their leader, the 1st Division captain and Captain-Commander, Genryūsai Shigekuni Yamamoto, for betraying them. The 2nd Division captain, Suì-Fēng, attempts to kill the traitors, but is stopped by Yoruichi, her former teacher. Furious that Yoruichi left her long ago, Suì-Fēng attacks Yoruichi, but fails to defeat her.

Suì-Fēng stops fighting and asks Yoruichi why she did not take her when she left. Ichigo and Byakuya fight, releasing their Bankai. With his Bankai, Ichigo's speed considerably increases, allowing him to overpower Byakuya. However, Ichigo cannot fully control his Bankai and as he is about to be defeated, his inner Hollow temporarily assumes control of his body. When Ichigo reverts to his normal state, Ichigo and Byakuya use their final attacks, leading to Ichigo's victory. Byakuya accepts his defeat and tells Ichigo that the reason that he permitted Rukia's execution was because the rules of his family are sacred to him. Meanwhile, Hitsugaya and Matsumoto discover that the entire Central 46 who ruled in favor of the execution are dead.

Hinamori discovers that Aizen is still alive, and proceeds to attack her with his Zanpakutō. Hitsugaya arrives; Aizen informs him that Gin was always his ally and co-conspirator in his scheme. Aizen easily defeats Hitsugaya. As the 4th Division captain, Retsu Unohana, arrives, Aizen explains that Soul Society has been under the effects of an illusion created by Aizen himself. Aizen goes to where Rukia is and says that he will be removing an object, called the Hōgyoku, from her body. This object, created by Kisuke Urahara, allows an individual to take the form of both Shinigami and Hollow. Ichigo, Renji and Komamura try to stop Aizen, but are easily defeated. After taking the Hōgyoku, Gin attempts to kill Rukia, but Byakuya intercepts the attack. As reinforcements from the Gotei 13 arrive, Aizen, along with Gin and Tōsen, escape by ascending into a dark rip in the sky facilitated by Menos Grande.

Aftermath
Aizen, revealed as a traitor, escaped with his cohorts Kaname and Ichimaru. Ichigo, Komamura, Renji, Byakuya, Hitsugaya, and Momo are all left in critical condition, but are healed by the skill of Orihime and Captain Unohana. Byakuya explains to Rukia why he acted the way that he did through the entire conflict and explained something about his and her shared past that she was until recently unaware of. Ichigo gained acceptance from the Gotei 13 for his role in stopping an injustice from taking place. In turn, he is made a Substitute Shinigami by Captain Ukitake and given leave to patrol his home town, Karakura Town.