The following contains spoilers for Jujutsu Kaisen Chapter 90, "The Shibuya Incident, Part 8" onward, by Gege Akutami, John Werry and Snir Aharon, available now in English through Viz Media.
Jujutsu Kaisen's Culling Game has been under way for a while, bringing with it vicious death matches and self-realizations for the Jujutsu Sorcerers involved. Protagonist Itadori Yuji and Fushiguro Megumi, two first-year students at Jujutsu High, have been taking part in the games -- but originally joined the brutal event with a shared goal: to free Gojo from the Prison Realm.
Itadori and Fushiguro hope to find the Angel, an incarcerated sorcerer using the body of Hana Kurusu as a vessel. The students seek the Angel's cursed technique, the only one known to be able to deactivate the Prison Realm and consequently free their beloved mentor, Gojo Satoru. However, foreshadowing in the Jujutsu Kaisen manga and anime suggests Gojo may be able to escape his entrapment without the help of any other sorcerers.
How Did Gojo Get Trapped in the Prison Realm?
Gojo has been sealed inside an inescapable realm since Chapter 90 of Jujutsu Kaisen, trapped by the ancient sorcerer Kenjaku whose goal is to create a new age of Jujutsu parallel to the Heian Period. To do this, Kenjaku entered Binding Vow's with countless cursed spirits and ancient sorcerers, unleashing them in the Culling Games to create a "battle royale" and produce enough cursed energy for him to merge with Tengen.
However, Kenjaku had to protect himself from the one sorcerer who could stop him: Gojo Satoru. To do this, Kenjaku possessed the corpse of Gojo's best friend, Geto Suguru. The wise sorcerer chose to inhabit Geto due to his powerful Cursed Spirit Manipulation technique, but using the alias of Gojo's closest one certainly shocked the strongest sorcerer into a state of submission. While Gojo was confused, Kenjaku successfully trapped him in Shibuya, keeping him out of the way ever since.
Gojo Could Sacrifice His Eye to Escape
Aside from the Angel's cursed technique, there were two other ways Gojo could be freed from the Prison Realm: the cursed weapon The Inverted Spear of Heaven, which Gojo destroyed while facing off with Toji Fushiguro, and Miguel's Black Rope, similarly destroyed by Gojo. Though, one fan theory suggests Gojo will escape the Prison Realm by sacrificing one of his eyes -- and in turn, his Six Eyes technique.
This theory stems from foreshadowing seen in the three Jujutsu Kaisen anime openings. In the first, Gojo is shown lifting his blindfold and revealing only his left eye. The second opening begins with a black cat (an animal commonly associated with bad luck) that looks back only with its left eye. In this same opening, Gojo is shown with his right eye covered by sunlight, once again revealing only his left.
Even in the mobile game, Phantom Parade, the opening has a sequence in which Gojo slowly looks up. When he looks back at the audience, glass shatters -- specifically over his left eye. Following this hefty foreshadowing, there are many scenes and panels in which Gojo is seen only revealing his left eye, adding more suspicion to this theory.
Gojo's Six Eyes Technique Could be Key to His Escape
Gojo's distinctive Six Eyes technique allowed him to master and use Limitless with complete control. It is also the only thing that makes Gojo an enemy to Kenjaku. In the past, Kenjaku lost twice to sorcerers of the Six Eyes, failing to defeat them even after killing the previous user less than a month after their birth. The user was able to reincarnate into another body, rendering the ancient sorcerer's efforts useless.
The Prison Realm appears to have a fixation with eyes, designed to be a cube with six faces similar to a die block, with a different number of eyes on each face. It works though the creation of a Binding Vow with its user, and once there is a victim, their only route of escape without being opened from the outside would be suicide. It's not far-fetched to suggest Gojo could escape the realm by creating a vow of his own and sacrificing one of his eyes.
Giving up an eye may be an ample sacrifice on par with the victim's death, as the Six Eyes technique is the source of much of Gojo's power. This would be an immense sacrifice to make and would make him abundantly less overpowered, so in theory it could be enough of a loss for the Prison Realm to release him.
Gege Akutami is renowned for his foreshadowing throughout Jujutsu Kaisen, so it's unlikely the imagery around Gojo's left eye is a coincidence. What this means exactly is yet to be revealed, but if Gojo Satoru does sacrifice an eye and lose his Six Eyes technique, it's likely he would not be strong enough to defeat Sukuna. How Gojo escapes the Prison Realm will undoubtedly be a turning point for the entire plot.