Invasion of Hueco Mundo

The  is a major conflict where Ichigo Kurosaki, Uryū Ishida, and Yasutora Sado enter Hueco Mundo in an attempt to rescue Orihime Inoue.

Prelude
After arriving in Hueco Mundo, Ichigo, Sado, and Uryū traverse the halls of an unknown structure. After setting off several traps, they are greeted by Demoura Zodd and Aisslinger Wernarr, two Arrancar under Sōsuke Aizen's command. Insisting Ichigo watch them fight, Sado and Uryū overpower the Arrancar, displaying their new abilities in the process. With the two Arrancar defeated, the room collapses, forcing the trio to escape outside.

Upon seeing Las Noches, they begin running towards it, impeded by the various natural hazards of the desert. Meanwhile, Aizen, gathering the Espada to inform them of the intrusion, stresses the intruders are not to be underestimated, but also not to be considered an immediate threat.

In the desert, Ichigo, Sado, and Uryū encounter three Hollows chasing a Human child, and decide to help the child. Ichigo learns the Human child is an Arrancar named Nel Tu. The three Hollows are her brothers, Pesche Guatiche and Dondochakka Birstanne, and their pet, Bawabawa. Afterwards, a Hollow named Runuganga attacks the group, and they are unable to harm him because his body is made of sand. They are saved by Lieutenant Renji Abarai and Rukia Kuchiki, who freezes Runuganga with her Shikai. Nel offers to take the whole group to Las Noches.

After breaking into Las Noches and finding themselves at a five-way fork, Ichigo's group splits up, each taking one path. Nel chases after Ichigo as Pesche and Dondochakka, forgetting the direction she took, travel down different paths. Meanwhile, Ulquiorra, making Orihime swear her loyalty to Aizen, explains to Espada Nnoitra Gilga the psychological traps Aizen created to ensure Orihime does not have the will to resist. Alone in her cell, Orihime recalls being taken to see Aizen by the Arrancar Loly Aivirrne and Menoly Mallia. Showing her the Hōgyoku, Aizen, claiming his revealing to her the location of the Hōgyoku is an act of trust, uses her powers to help him restore the Hōgyoku, claiming it has been a little damaged from use. Resolving to destroy the Hōgyoku by erasing its existence, Orihime claims it is something only she can do. As Orihime plans to derail Aizen's plot, Aizen sits in thought in his room.

Early Stages
When Ichigo and Nel encounter the Privaron Espada Dordoni Alessandro Del Socaccio, Ichigo begins to battle him. Sado and Uryū each encounter an Arrancar, and former Shinigami captains Gin Ichimaru and Kaname Tōsen observe the battles through the surveillance system in Las Noches. Though Ichigo and Dordoni fight evenly, Dordoni gains the upper hand by releasing his Zanpakutō, overpowering Ichigo, and demands Ichigo use his Bankai. When Ichigo refuses, Dordoni fires a Cero in response. Swallowing the blast, Nel fires it back at Dordoni, who attacks her. When Ichigo uses his Bankai to stop the attack, Dordoni requests Ichigo use his Hollow powers to fight him. Donning his Hollow mask, Ichigo disables Dordoni with a single strike. As Nel heals Dordoni with her saliva at Ichigo's request, Dordoni reveals he had hoped to regain his position as a full Espada by defeating Ichigo at full power. After being completely healed, he attacks Ichigo again. After being struck down by Ichigo once again, Dordoni thanks Ichigo for using his full power against him by fighting the Exequias, a group of Arrancar specializing in eliminating intruders, to allow Ichigo to retreat. When Aizen learns of this, he asks who ordered the Exequias to attack Ichigo, and the Espada Szayelaporro Granz takes responsibility. Forgiving him, Aizen notes Dordoni's body will help Szayelaporro's research. Meanwhile, Uryū is battling the Privaron Espada Cirucci Sanderwicci.

In his battle with Cirucci, Uryū finds his attacks continuously blocked by Cirucci with the aid of her Zanpakutō. As the battle continues, Pesche, appearing, decides to help Uryū. Pesche uses Infinite Slick, causing Cirucci to trip and land awkwardly on the ground. Incensed, Cirucci releases her Zanpakutō, Golondrina. Unable to counter her abilities with his arrows alone, Uryū pulls one of the tubes from his belt, which produces a powerful energy blade that slices through her winged blades. With his energy sword, which he calls Seele Schneider, Uryū defends himself against Cirucci's attacks. In response, Cirucci, shedding her wings, focuses all her power into a single blade on her tail, and Uryū defeats her by shooting his Seele Schneider from his bow into her chest. As Uryū and Pesche leave, the Exequias arrive to kill Cirucci.

Elsewhere, Sado finds himself at a disadvantage against the Privaron Espada Gantenbainne Mosqueda. After taking several blows, Sado, realizing how to access his full power, transforms his right arm into a giant shield named Brazo Derecho del Gigante. With his full power unleashed, Sado overpowers Gantenbainne, who releases his Zanpakutō, Dragra, in response. Revealing his right arm is intended solely for defense, Sado, transforming his left arm, names it Brazo Izquierdo del Diablo. With his left arm, Sado, defeating Gantenbainne, allows him to live. Confronted by Nnoitra, Sado fruitlessly attacks Nnoitra with his left arm, prompting Nnoitra to defeat Sado with a single attack.

Middle Stages
Bored with the ease of his victory, Nnoitra leaves to pursue another intruder. Sado's apparent death is felt by everyone in Hueco Mundo, and when Ulquiorra brings dinner to Orihime, she refuses to believe Chad has died. Admonishing her, Ulquiorra notes that all her friends are doomed to fail because they rushed into battle without realizing the odds they faced. Slapping him, Orihime bursts into tears after Ulquiorra leaves. Elsewhere, Rukia encounters the Noveno Espada Aaroniero Arruruerie as Gin manipulates corridor controls. Removing his mask, Aaroniero reveals the face of Shinigami Kaien Shiba, the former lieutenant of the 13th Division, whom Rukia killed. Conversing with Aaroniero, Rukia believes he is the real Kaien. Kaien states after he was killed, he was resurrected in Hueco Mundo, where he became one of Aizen's Espada. Kaien offers Rukia a chance to atone for killing him by allowing him to kill her, and Rukia accepts, with the understanding she will be allowed to rescue Orihime. Revealing he was joking, Kaien instead instructs her to kill all of her friends. Realizing he is an impostor, Rukia begins to fight Kaien, who gains the upper hand because he was the one who taught Rukia how to fight. Meanwhile, Renji and Dondochakka encounter Szayelaporro. When Renji attempts to use his Bankai, it shatters, prompting Szayelaporro to reveal he designed the room they are in to negate Renji's Bankai.

Rukia continues to struggle against Kaien, who begins to overpower her when he uses the Shikai of his Zanpakutō. When Kaien disarms her, Rukia, attempting to use a Kidō spell, reveals in the process Kaien is afraid of the sunlight. Armed with this knowledge, Rukia, binding Kaien with Kidō, blasts a hole in the wall. In the sunlight, Kaien's face melts away to reveal a glass case with two masks inside. The creature reintroduces himself as Aaroniero, and, after moving out of the sunlight, assumes Kaien's appearance again. After informing Rukia he absorbed Kaien's remains when he came to Hueco Mundo, Aaroniero releases his Zanpakutō, Glotonería. Overwhelmed by Aaroniero's released form and the realization that he possesses Kaien's actual body, Rukia is impaled through the stomach, and her Zanpakutō, Sode no Shirayuki, is broken in the process. Recalling her training with Kaien, she, regaining her resolve, reconstructs her Zanpakutō with ice and impales Aaroniero through the head. As Aaroniero dies, Rukia, attempting to stand in order to continue her journey to save Orihime, collapses from her injuries. All of the Espada sense Aaroniero's death.

Meanwhile, Renji questions Szayelaporro on how he negated his Bankai. Szayelaporro reveals he gathered the data using parasites stored in the body of his older brother, Yylfordt Granz, whom Renji fought and defeated. With only his Shikai, Renji's attacks cannot harm Szayelaporro. They are interrupted by two of Szayelaporro's Fracción, Lumina and Verona, who inform Szayelaporro of the death of Aaroniero. Admitting he missed the death in his preoccupation with Renji, he relays the information of Rukia's death to Renji, who proceeds to furiously renew his attacks against him. Blocking his Shikai, Szayelaporro states without a Bankai, he cannot win. Putting more force behind his attack, Renji, injuring him, tells Szayelaporro to get out of the way.

Elsewhere, Ulquiorra meets Ichigo to inform him of Rukia's death. As Ichigo attempts to leave to save Rukia, Ulquiorra goads him into fighting by revealing he was the person who forced Orihime to come to Hueco Mundo. Furious, Ichigo, activating his Bankai, dons his Hollow mask. Even after using his most powerful attacks, Ichigo is overpowered by Ulquiorra. Refusing to give up, Ichigo believes Ulquiorra to be the top-ranked Espada. Ulquiorra reveals his "4" tattoo, indicating he is the Cuatro Espada, and stabs Ichigo in the chest with his hand, telling Ichigo to either escape from Hueco Mundo or die.

With Ulquiorra away fighting Ichigo, Loly and Menoly, blasting open the door to Orihime's cell, confront her. Furious because Aizen favors Orihime over them, the two female Arrancar begin to physically abuse Orihime, who, refusing to fight back, says she is there to serve Aizen. As Loly grows increasingly violent, despite Menoly's objections, Grimmjow Jaegerjaquez, arriving, kills Menoly and grievously injures Loly. Telling Orihime his actions were motivated by his desire to repay Orihime for restoring his arm, he, asking her for another favor, takes her with him. Before they leave, Grimmjow tells Orihime to heal her injuries, but Orihime uses the opportunity to heal Loly and Menoly.

Elsewhere, Uryū arrives just in time to aid Renji as the latter starts to be overwhelmed by the numerous Fracción of Szayelaporro. Pleased by the appearance of Uryū, Szayelaporro, revealing he has already obtained a record of Uryū's Reiatsu from Cirucci, adjusts the room so Uryū finds his attacks useless against both the Espada and his Fracción. After Renji saves Uryū from a fatal blow, the two prepare to work together to take down their common foe. With Renji's help, Uryū, maneuvering Szayelaporro into a trap, catches him in a massive explosion. Though the trap is damaging, it fails to kill Szayelaporro, who, eating one of his Fracción, Lumina completely heals himself. Rather than retaliate, he leaves, wanting to replace his damaged clothing and allow Renji and Uryū to formulate a new plan.

Meanwhile, Grimmjow, bringing Orihime to Ichigo, tells her to heal Ichigo, but before she can finish doing so, Ulquiorra interrupts them, having learned from Loly and Menoly Grimmjow had taken Orihime. Using a Caja Negación, Grimmjow, trapping Ulquiorra in an alternate dimension, states it will take several hours for Ulquiorra to break free. Grimmjow orders Orihime to continue healing Ichigo, but Orihime refuses, having learned Grimmjow just wants Ichigo healed so he can fight and hurt Ichigo again. When Grimmjow lashes out at Orihime, Ichigo, stopping him, asks Orihime to heal both himself and Grimmjow so they can settle their battle once and for all, which Orihime does.

As Ichigo and Grimmjow begin fighting, Ichigo finds himself outmatched despite using his Bankai. Forced to don his Hollow mask in order to block a Gran Rey Cero Grimmjow fires at Orihime and Nel, Ichigo, noticing Orihime's discomfort with his Hollow appearance, is emotionally shaken. Pleased Ichigo is fighting with his full power, Grimmjow releases his Zanpakutō, Pantera. As the two continue their fight, Ichigo is slowly worn down by Grimmjow despite being able to use his Hollow mask longer than he previously could. Tercera Espada Tier Harribel and her Fracción - Emilou Apacci, Franceska Mila Rose, and Cyan Sung-Sun - watch the fight from afar. Telling them it is natural for them to be afraid of Grimmjow and Ichigo, Harribel states it is more like a fight between two Espada than anything else. Frightened by Ichigo's appearance due to his Hollow mask, Orihime is afraid to watch the battle, but after Nel admonishes her, she, overcoming her fear, cheers Ichigo on. When Ichigo, stopping Grimmjow's attacks bare-handed, cuts him across the chest, a wounded Grimmjow, refusing to give up, uses his strongest attack on Ichigo, who, overcoming it, deals a final blow. As Grimmjow falls to the ground, Ichigo, catching him, gently lowers him to the ground. Having dealt with Grimmjow, Ichigo prepares to take Orihime away from Las Noches.

End Stages
As Ichigo brings Orihime down from the tower on which he left her, a heavily injured Grimmjow, appearing before him, demands Ichigo continue their fight even as his Resurrección involuntarily dissipates. As Ichigo, refusing, casts away his sword as he attempts to reason with Grimmjow, they are interrupted by Nnoitra, who attacks Grimmjow to get him out of the way. Intervening, Ichigo protects Grimmjow as Nnoitra moves to finish him off. As Tesra Lindocruz recaptures Orihime, Ichigo starts to fight Nnoitra, who reveals he is the Quinto Espada, and is therefore stronger than Grimmjow. Nnoitra overpowers the tired Ichigo, and when Orihime attempts to help, Tesra threatens to destroy her hairclips, the source of her power which would allow her to stop Tesra. As Ichigo continues to fight, Nnoitra, encountering Nel Tu, recognizes her. He reveals her true name is Nelliel Tu Odelschwanck, and she is a former Espada.

Meanwhile, Renji, Uryū, Dondochakka, and Pesche attempt to flee, but because Szayelaporro controls the building they are in, he redirects the hallways to point back towards their battlefield. Releasing his Zanpakutō, Fornicarás, he creates clones of Renji, Uryū, Dondochakka, and Pesche. Though he releases the power limiter in the room to allow Renji and Uryū to fight at full power, they struggle to fight the clones, who keep copying their attacks and movement.

Nnoitra uses Nel as a shield against Ichigo, whom he pins to the ground. As he prepares to break Ichigo's arm, the intensity of Nel's emotions causes her to return to her original adult form, Nelliel. Taking Ichigo away from the battlefield, Nelliel, preparing to fight Nnoitra, reveals she was the former third Espada. As they begin to fight, Nnoitra states he despised Nelliel even during her time as an Espada. As she starts to overpower Nnoitra, he fires a Cero. Using Cero Doble, Nelliel, absorbing Nnoitra's Cero, fires it at him with doubled force. Emerging relatively unharmed, Nnoitra reveals the Espada have grown stronger in her absence.

As Nnoitra taunts Nelliel about their past, Nelliel releases her Zanpakutō, Gamuza. As Nelliel, overwhelming Nnoitra, attempts to finish him off, she transforms back into her child form. As Ichigo tries to help Nel, Nnoitra allows Tesra to fight him. After releasing his Zanpakutō, Verruga, Tesra starts to torture the exhausted Ichigo. Before Tesra can deal the final blow, he is stopped by the unexpected arrival of 11th Division Captain Kenpachi Zaraki.

Back in Szayelaporro's lab, as Renji uses his Bankai, the clones copy him, destroying the building. In response, Szayelaporro, destroying the clones, uses another ability of his released form to create voodoo dolls of his opponents. Using the dolls, he inflicts pain on his targets and damages their internal organs. Meanwhile, sensing Nel was engaged in battle, Pesche and Dondochakka fight Szayelaporro in an attempt to end the battle quickly so they can go assist Nel. They use Cero Sincrético to attack Szayelaporro, who, nullifying the attack, reveals he has already analyzed their spiritual energy. As the situation turns desperate, 12th Division Captain Mayuri Kurotsuchi arrives with his lieutenant, Nemu Kurotsuchi.

Defeating Tesra in a single blow, Kenpachi tells Ichigo to stay out of his fight with Nnoitra. He tells Ichigo Kisuke Urahara was tasked with making the Garganta gateways into Hueco Mundo stable enough for Shinigami captains to enter, and three other captains went with him. As Captain Retsu Unohana arrives with her lieutenant, Isane Kotetsu, they stop the Exequias from killing Gantenbainne and Sado. As Mayuri and his lieutenant Nemu arrive, Mayuri is confident he can win against Szayelaporro, even after Szayelaporro creates a voodoo doll of him. Arriving to save Rukia from the Séptima Espada Zommari Rureaux, Captain Byakuya Kuchiki overcomes Zommari's enhanced speed with the techniques Yoruichi Shihōin taught him. Even after Zommari releases his Zanpakutō, Brujería, Byakuya, overcoming his opponent, defeats him.

Activating his Bankai, Mayuri defeats his opponent. Reviving himself from inside Nemu's body with Gabriel, Szayelaporro claims because of this ability, he is the perfect being. Revealing Szayelaporro has been infected with the superhuman drug he put inside Nemu's body, Mayuri finishes him off while explaining there is no such thing as perfection. Discovering Szayelaporro's laboratory in the rubble, Mayuri finds a pair of hanging bodies. As Rukia regains consciousness, Byakuya tells her there are more battles to come. As Kenpachi slowly begins overpowering Nnoitra, his opponent, becoming desperate, knocks his eyepatch off by mistake. After being completely overwhelmed, Nnoitra, releasing his Zanpakutō, Santa Teresa, gains an advantage. Deciding to use Kendō, Kenpachi defeats the Espada. As Nnoitra dies, he recalls his past on how he wants to defeat any opponent he comes across, or at least be killed by someone stronger than him. After Nnoitra's death, Coyote Starrk, arriving, takes Orihime back to Aizen.

Aftermath
Revealing to the invaders of Hueco Mundo he used Orihime to lure Ichigo and his friends to Hueco Mundo to deprive the Gotei 13 of their new military asset, the substitute Shinigami, Aizen delights in being able to trap four of the Gotei 13's remaining ten captain in Hueco Mundo as he himself launches his counter-invasion of Karakura Town. Having anticipated his invasion, the Gotei 13 face him when he arrives in Karakura Town, which the Gotei 13 replaced with a fake in order to keep it and its inhabitants safe.