A while ago,
Sōsuke Aizen, Kaname Tōsen, and Gin Ichimaru prepare to leave for the Human World, along with the top three Espada and their Fracción, to destroy Karakura Town and create the Ōken, Aizen telling Orihime Inoue to wait there until they finish destroying Karakura Town.
Before they depart, Ulquiorra Cifer breaks free from the Caja de Negacion to protect Las Noches in Aizen's absence.
Upon leaving Hueco Mundo, Aizen found out that Captain-Commander Genryūsai Shigekuni Yamamoto and the remaining captains were standing guard in a fake Karakura Town.
Aizen, aware it is a fake, states he will simply defeat them here and create the Ōken in Soul Society. Summoning his remaining forces to the field to battle the Gotei 13, he is caught by Yamamoto's Jōkaku Enjō.
As the Captain-Commander gives the order, the battle begins.
Later, during the battle between Lieutenant Rangiku Matsumoto and Tier Harribel's Fracción, the former is saved by the timely arrival of Lieutenant Momo Hinamori.
Soon after, Harribel's Fracción use Quimera Parca to summon the behemoth Ayon, who begins overwhelming the lieutenants.
Defeating the beast, Yamamoto incapacitates Franceska Mila Rose, Cyan Sung-Sun, and Emilou Apacci.
Later, Harribel, stirred by the defeat of her comrades, gets serious in her fight with Captain Tōshirō Hitsugaya while Captain Shunsui Kyōraku faces off against Coyote Starrk, who reveals himself as the Primera Espada.
As Captain Suì-Fēng and Lieutenant Marechiyo Ōmaeda prepare to face off against Baraggan Louisenbairn, all three Espada begin to exert their Reiatsu, sending shockwaves across the battlefield.
…
Meanwhile back at los noches in Hueco Mundo, Ulquiorra, speaking to Orihime, asks her if she is afraid.
Recalling the events leading up to this point, she states she is not afraid, for her heart is with her friends.
Questioning her statement, Ulquiorra is interrupted by Ichigo Kurosaki smashing through the floor to arrive where Ulquiorra and Orihime are.
As he tells Ulquiorra to step away from Orihime, Ulquiorra unsheathes his sword, much to Ichigo's surprise, and they begin to clash while Orihime looks on.
Ichigo has sustained a minor cut from Ulquiorra's sword. Ulquiorra stands put, waiting for Ichigo's charge. When the charge comes, the fight begins in earnest.
Back outside, near the ruined outer wall of Las Noches, Renji and Chad are busy fending off a horde of low-level Hollows.
Renji, who finds it difficult to fight alongside the uncommunicative Sado, asks him to warn him before launching his attacks.
On the top of the wall, Rukia Kuchiki has finished off all of the Exequias.
She now faces Rudbornn Chelute, who informs her that defeating his subordinates doesn't mean a thing, as he releases his Resurreccion, Arbol. Rukia is distracted by an explosion tearing through the wall of the tower where Ichigo and Ulquiorra are fighting.
Ichigo and Ulquiorra seem more or less evenly matched, but Ulquiorra shows better resolve and is able to maneuver Ichigo into a defensive position.
Ulquiorra blocks Ichigo's Getsuga Tenshō; he then uses Sonído to get behind Ichigo and, after several missed jabs, manages to pierce Ichigo through the shoulder and immediately shoots him with a Cero.
Ulquiorra's Cero blasts through the tower wall.
Ichigo is injured and visibly dizzy from the Cero hit, but Ulquiorra acknowledges that he was able to withstand it without using his Hollow mask.
He notes that Ichigo is stronger and asks if it is because of his fight with Grimmjow Jaegerjaquez, because of his friends or because of Orihime.
Glancing at her, Ulquiorra says Orihime is one with the Arrancar now and that saving her would be pointless. Ichigo dismisses his words, saying he is not the one to determine that. Ulquiorra agrees, saying this decision is for Sōsuke Aizen to make.
Ichigo finds himself on the receiving end again, dodging more blows than he is sending, but as he does, he begins to realize that he can read Ulquiorra's attacks and moves much better than before. He focuses on Ulquiorra's hand movements and eventually manages to grasp his wrist, which he follows with a slashing attack to Ulquiorra's chest.
Ichigo's attack left a long but shallow cut across Ulquiorra's chest. Ichigo asks if that is thanks to his Hierro but remarks that he can now read Ulquiorra's motions much better, whereas during their first fight he couldn't read them at all.
Ichigo wonders aloud if this is due to himself becoming more like a Hollow, or because Ulquiorra has grown more like him. This statement serves to aggravate Ulquiorra a great deal, manifested in him stabbing the ground with such force that it breaks and rises in two heaps to Ulquiorra's left and right.
As a surprised Ulquiorra sees his sword crack under Ichigo's assault, Ichigo's Getsuga Tenshō pushes Ulquiorra through the tower wall. As he falls, he fires a Cero at Ichigo, who blocks it with Tensa Zangetsu.
Convinced his attacks no longer have any effect on Ichigo, Ulquiorra flies upwards past Ichigo. As Ichigo follows, Ulquiorra, cutting through the dome of Las Noches, lands atop a high pillar.
Ulquiorra reveals there are two things forbidden inside the walls of Las Noches: the use of the Gran Rey Cero, and the release of any of the top four Espada's Zanpakutō, for those are powerful enough to destroy the building.
Releasing his Zanpakutō, Murciélago, he advises Ichigo to stay constantly alert and never let his guard down, even for a single second.
Materializing a javelin, he, using Sonído, appears in front of a surprised Ichigo, who has barely any time to react.
As the severity of the attack leaves Ichigo wounded and kneeling, Ulquiorra, stating Ichigo fired a Getsuga Tenshō instinctively, coldly compliment him on doing so, for had he not done so, his head would be rolling at Ulquiorra's feet.
With the upper-right portion of his mask gone, Ichigo gasps as he turns his head to face his attacker, who coldly stares back at the wounded Ichigo.
...