Sosuke Aizen’s drive to put an end to the Soul King comprised most of the drama in Bleach and in the Arrancar Arc. The former Captain of the 5th Division, who betrayed the Soul Society to become a “true transcendent being”, failed in his mission when he was defeated by Ichigo’s Final Getsugatensho. A question that still remains unanswered is whether or not the Hogyoku rejected Aizen, bringing an end to his tyranny and ambition of not being controlled.
The Hogyoku, created by Aizen and Urahara, is a bluish orb similar to the Heart of the Soul King that manifests the desires of the user into reality by breaking the division between Hollows, Soul Reapers, and Reapers. It gives the possesser infinite strength. However, it has a will of its own similar to a parasite – transforming the host’s body whenever into something more demonic and powerful as seen in the Ichigo versus Aizen fight.
During his fight with the combined forces of Kisuke Urahara, Yoruichi Shihoin, and Isshin Kurosaki, Aizen mentioned that he has “subjugated” the Hogyoku rather than fusing with it. It is worth mentioning that he revealed the fact when he had his guard down and wasn’t playing any mind games. He eventually fulfilled his wish of transcending the boundaries of Soul Reapers and Hollows, fusing with his Kyoka Suigetsu Zanapakuto but got sealed in the process due to possessing a condition-based Kido by Urahara.
Many Bleach fans wonder why the Hogyoku rejected Sosuke Aizen. After all, the Thousand Year Blood War Arc saw the villain exceed the boundaries of his strength once again even though he was strapped to a chair in the Muken, the lowest level prison. Sosuke would have easily broken through Urahara’s Kido if he ‘willed it to the Hogyoku.’ He even completed his fusion with Kyoka Suigetsu and Hogyoku – a power that generalizes him as the Main Villain in Bleach rather than the Quincy Emperor.
There are two interpretations of why the Hogyoku rejected Sosuke Aizen and all two point out that it never truly did. According to fan theories, Ichigo planted a ‘doubt’ in the mind of Aizen about his own power by splitting him into two with Mugetsu. This activated Urahara’s Kido, which many believe was implanted during the Senju Koten Taiho release. Sosuke’s fears of being defeated got manifested by the Hogyoku and the rest is history.
Another interesting theory is that Sosuke Aizen himself wanted to be defeated. As pointed out by Ichigo a few episodes after Aizen’s defeat, he sensed ‘loneliness’ when he touched Kyoka Suigetsu. Sosuke would have been disillusioned by the powers gained by the ‘Ryoka boy’, someone whose whole life journey he had planned, and how his elaborate plan paled in comparison to Ichigo’s natural growth as a Shinigami.
Another reason why the Hogyoku never rejected Sosuke Aizen revealed in Bleach: Thousand Year Blood War
“Everything is going according to plan.” While many fans consider Sosuke Aizen beaten by his own game by Kisuke Urahara’s cunning, the eventual winner turned out to be Aizen. The former Captain always had a backup plan if things went south and he may have envisioned his defeat despite possessing godlike powers.
Somehow, Aizen’s stay in the Ouken for over 100 years made him more powerful than before. This further signifies that the Hoyoku embedded in his chest is functioning as per its master’s wish. A glimpse of his powers was seen during his meeting with Kyoraku Shunsui, when a few guards were foolish enough to try to bind Aizen once again and got cut down by his Reiatsu. Sosuke even performed a Hado 99:Goryūtenmetsu without any incantation against Ywach.
Based on the fan theories belonging to the “Sosuke Aizen chose to be defeated” scenario, the mastermind did so to increase his powers and gain some introspection while being imprisoned. Many fans theorize that he chose to stay dormant in the Muken to wait for Ywach and finish him to protect Soul Society to fulfill his ultimate goal – not being controlled by either the Soul King or Ywach, or any other entity.
It was believed that Tite Kubo was formulating Sosuke Aizen to be the Final Boss after Ywach’s defeat but that didn’t pan out. Given the massive fan-following backing the villainous Aizen to regain control of the Soul Society, we might see another arc in the development… in the next ten years!