Having also framed Kisuke for the Vizards' creation and forced his exile, Aizen learned the Hōgyoku actually grants its user's desires if they have the will to carry it out.

Aizen continued experimenting on Soul Reaper/Hollow hybrids with his creations Metastacia and White, playing a respective role between Rukia Kuchiki and those of Isshin Shiba and Masaki Kurosaki.

From there, Aizen appropriates Barragan's palace Las Noches and reconstructs it in his own image, recruiting Tier Halibel and other Arrancars that would become his Espadas.

Originally, Aizen carried a zanpakutō called Kyōka Suigetsu (鏡花水月, literally "flower in the mirror, moon on the water").

However, Squad 4 Captain Retsu Unohana uncovered the truth, as Aizen removed the Hōgyoku from Rukia, before he, Gin and Tōsen escape into Hueco Mundo.

From there, Aizen begins to make several Arrancars in his service stronger using the Hōgyoku and sends some of his Espadas to the Land of the Living to gain information on Ichigo.

However, sacrificing the weakest members of the Espadas in the process, Aizen revealed the kidnapping as a distraction for Ichigo and as part of a scheme to cut the Soul Society's forces in half by the time he enacts his attack on Karakura Town.

Though he came with three of his strongest Espadas, the defeat of Staark and Baraggan convinces Aizen that he has surpassed his own minions and strikes Halibel down to deal with the opposition personally.

Aizen makes his way to the Soul Society so that he can create the Ōken, finding Ichigo's school friends and deciding to kill them first before enacting his goal.

Though expecting him not to be a threat due to his sudden lack of spirit energy, Aizen finds himself overwhelmed by Ichigo's newly enhanced physical strength.

Though his fear caused the Hōgyoku to turn him into a Hollow-like monster, Aizen barely survived Ichigo's final attack as he evolved once more to the point that he became immortal.

However, Ichigo's attack weakened and defeated Aizen to the point that the Hōgyoku no longer acknowledges him as he is reverted to his human form while engulfed in a specially made kidō "Seal" that Urahara planted on him.

Later, when the Wandenreich invade the Soul Society, Yhwach asks Aizen to join up with them, but he refuses and delays the time sufficiently in conversation and he is forced to retreat.

He remarks while people could go through life simply living, it does not compare to courageous individuals like Ichigo, who is willing to face death and cut through fate without fear.

[6] Initially a character that had "an excellent balance between being cool as hell and incredibly detestable", Aizen eventually "stopped bothering to devise clever schemes and instead relied purely on his own immense strength to get the job done.

"[6] More positive was Carlo Santos from the same site who believed Aizen's character had grown "deliciously cruel" and that his ability to match the entirety of Soul Society via constantly-shifting technique made his battles "impossible to be bored with".

He wrote that "when Aizen was defeated, the story felt finished" and that "a ton of people stopped reading at that point, even though it was widely known that the series would be continuing anyway".