One of the most important arcs in all of Bleach is the Hueco Mundo Invasion story arc, the third arc in a set building up to the final battle with the villainous Sosuke Aizen. The arc is a major game-changer for the series, taking the characters and plot in a completely new direction, while amping up the stakes and the level of power in play.
The arc picks up after the Arrancar, Aizen's unmasked Hollow minions, have already laid siege to Karakura Town and abducted Orihime Inoue. The leaders of Soul Society refuse to help, so protagonist Ichigo Kurosaki takes it upon himself to storm Hueco Mundo, the home dimension of the Hollows, to rescue Orihime on his own. But, he wouldn't be alone for long.
A United Front
A major theme of the Hueco Mundo arc is unity. Throughout the arc, many different people and factions come together to protect the world and defy Sosuke Aizen's mad schemes. Ichigo was prepared to invade the Hollow realm alone but, by the time he reached Kisuke Urahara's shop to step into the portal, his friends Chad - a fellow human - and Uryu Ishida - a Quincy - were adamant on helping him, no matter what. As a Quincy - a spirit medium that opposes the Soul Reapers - Uryu is supposed to be Ichigo's bitter rival, but he too is a friend of Orihime's, and he won't let Aizen or anyone else hurt her. So, the three friends storm the desert world of Hueco Mundo together.
While trekking across the endless desert, Ichigo also comes across a tiny Arrancar named Nel, as well as her large friends Pesche, Dondochakka and Bawabawa. Despite being Arrancar, Nel and company aren't hostile, and are happy to help Ichigo's team cross the desert to reach Las Noches, Aizen's mammoth fortress. However, just as the group gets close, a sand-dwelling Hollow traps them in a pit, and all seems lost until Rukia and Renji arrive.
Though Soul Society's leaders refused to help, Captain Byakuya Kuchiki gave these two Soul Reapers his blessing to sneak off and help rescue Orihime. Rukia and Renji are old allies of Ichigo's and, with their help, the team escapes the sand trap and breaks into Las Noches to begin the rescue operation. From here, they split up to cover more ground but, before they go, Renji performs a battle chant to harden everyone's resolve, uniting human, Soul Reaper, Quincy and Arrancar in this singular mission. And the villains are waiting for them.
Powerful Villains And The Big Trick
Ichigo's team soon faces its biggest challenge: the Espadas, the ten strongest Arrancar. These powerful foes are unlike anything Ichigo and company have ever faced before, and the challenges grow steeper these heroes finally enter Las Noches. Rukia defeats Aaroniero, the 9th Espada, but nearly loses her life and is in no shape to continue. Chad, meanwhile, defeats another villain before succumbing to Nnoitora Gilga, the vicious 5th Espada. And Ichigo, Renji, and Uryu have it even worse.
Grimmjow Jaegerjaques, the 6th Espada, enters the scene eager to fight, even breaking Orihime out to help him in his selfish mission. Ichigo defeats the low-ranking Privaron Espada Dordoni, only to be killed fighting the 4th Espada, Ulquiorra Schiffer. Grimmjow wants a fair fight, though, and tells Orihime to revive Ichigo and heal him. He and Ichigo then have their final duel, with Ichigo eking out a win.
Ichigo's victory is short-lived, however, as Nnoitora arrives just in time to beat him within an inch of his life. Uryu and Renji, meanwhile, struggle against the 8th Espada, Szayelaporro Grantz, and not even the power of their Arrancar allies is much help. All seems lost, until four Captains show up: Zaraki, Kuchiki, Unohana and Kurotsuchi.
These Captains finish off the 5th, 7th and 8th Espadas, and it seems like Ichigo's mission is back on track. He even has Orihime by his side, until the 1st Espada, Coyote Starrk, abducts her again. Following this, Aizen makes an announcement across Las Noches. Everything up to this point was a ruse to trap these powerful heroes in the fortress, and he immediately seals off all exit portals. Now, the group can only watch as Aizen and his remaining followers storm Karakura Town to complete the last step of his plan.
The Hueco Mundo Invasion arc hosts some of the best battles in Bleach, with the fights against the Espadas, and proves that a united team is better than one man acting al0ne. Most of all, it is a springboard for the final step in Aizen's plans, and the stakes and odds are at their highest as Ichigo rushes back to Karakura Town to save the day.