Seeing Sukuna confined inside a seemingly endless row of rib cages and mountainous skulls gives off the impression that he is sealed and is just waiting for the perfect time to be released. Given how highly everyone is evaluating him, it is unlikely for Sukuna to just sit around without doing anything especially since we witnessed how bloodthirsty he is from the brief control he had over his vessel’s body from episode 2 of the anime. But who sealed Sukuna?
When was Sukuna Sealed?
Sukuna died and became a Cursed Object one thousand years ago during the heyday of curses. His consciousness along with the fragment of his curses is sealed inside the Cursed Object.
Who Sealed Sukuna? Two Popular Opinions
1. Kenjaku sealed Sukuna’s soul inside the Cursed Object through Binding Vow.
One interesting theory is that Sukuna agreed to a binding vow with Kenjaku to make him a Cursed Object that’s why his fingers remain after his death. As we all know, both Sukuna and Kenjaku are individuals from a thousand years ago. And Kenjaku is seen hanging around with Uraume, a loyal retainer of Sukuna. And for the past thousand years, Kenjaku has been making Binding Vows with different Jujutsu Sorcerers and Curse Users. The agreement in the contract is that they will remain in deep slumber as a Cursed Object and incarnate to their respective vessels at the start of the Culling Game.
But, Sukuna immediately took control of the body of his vessel (Yuji) after consuming the finger although Yuji regained control afterward. This means that either Sukuna doesn’t have a contract with Kenjaku and he became Cursed Object naturally or a loophole was created in the contract since Sukuna’s Cursed Object split into twenty fingers so technically Sukuna doesn’t fully incarnate.
2. Sukuna wasn’t sealed in the first place.
After Sukuna’s death a thousand years ago, a finger remains that contains his curse. And since Sukuna is an object of fear known as the “Demon God” with four hands and two faces, Sukuna became the curse he represents when he was still alive after his death.
The Sukuna’s Finger which contains his curses splits into twenty fingers. Inside each of these fingers is the sleeping fragmented soul of Sukuna along with a portion of his power. These indestructible fingers traverse generations in wait for the suitable vessel to incarnate himself.
And when Yuji Itadori, a suitable vessel, consumes one of the fingers, all of the fragmented souls of Sukuna awaken. The fragment of the soul that resides within the finger that Yuji consumes momentarily takes control of Yuji’s body.
But when Yuji asserts his dominance over his body, Sukuna’s soul is pushed back into a subspace created by his Innate Domain or the “Inner Self”. Sukuna is completely integrated with his vessel so they can’t be separated anymore (just with the fingers that Itadori ingested as well as the fragment of Sukuna’s consciousness within those ingested fingers). Sukuna can’t take control of the body nor leave the vessel so he just stayed in his Innate Domain while waiting for the opportunity to take over.
Supposedly, the scenario should go like this; when an unsuitable vessel consumes the finger, it will immediately die due to poison and curses of Sukuna’s Finger. On the other hand, if a suitable vessel consumes the finger, Sukuna will take over control of the body and he will extinguish/ kill the consciousness of the vessel. One finger is enough to overpower a vessel since one finger is almost equivalent to a Special Grade Cursed Spirit and Sukuna’s soul will undoubtedly be firmer than the vessel’s.
After Sukuna takes over the body, he will start collecting and consuming the remaining fingers to incarnate fully. But, this obviously didn’t happen since Yuji is an unforeseen variable that maintained control over his body.
How Was Sukuna Sealed?
Sukuna is the strongest in his day, way back to thousand years ago. His notoriety reached the entirety of Japan earning him the fearsome moniker of “Demon God” with two faces and four hands. He became a legendary object of fear even though he was still alive which begs the question, how was Sukuna sealed? Let’s find out different possible scenarios.
1. The entirety of Jujutsu Sorcerer Society banded together to defeat him
We know that even though Jujutsu Sorcerer Society shares a common enemy, Cursed Spirits and Curse User, there is still a faction that divides it. Different clans/ families aim to be the leading most prominent houses in Society. They vary in beliefs and traditions which resulted in many conflicts throughout history.
And given how Sukuna’s moniker is widely feared throughout the entirety of Japan with most normal humans fearing him as the Demon God, different clans and families banded together in order to kill him. Furthermore, that was one thousand years ago, the heyday of curses. There will surely exist different sorcerers with exceptional Cursed Techniques like “The Angel” who can erase Cursed Technique.
2. There is a traitor among his subordinates
Based on what is shown in the techniques of Sukuna so far, we can clearly conclude that his Techniques are optimized for solitary and deathmatch battles. His Domain Expansion alone can obliterate thousands of first-grade Jujutsu Sorcerers since he can stretch it out up to kilometers in radius and slice everyone within it. And given Sukuna’s personality, it is clear that he doesn’t depend on other people to protect him or help him in battle. This means that he really is an unstoppable force and a disaster in himself.
So, bringing a lot of Jujutsu Sorcerers doesn’t guarantee an advantage since Sukuna can cut down anyone in one fell swoop depending on toughness and Cursed Energy. That’s how this theory comes forth. There is a traitor among the followers of Sukuna that caused Sukuna’s downfall. Even though Uraume is the only known subordinate of Sukuna, we can’t rule out the possibility that there are other people willing to serve under him.