Sukuna/Synopsis

History
Over a thousand years ago, Sukuna was a human sorcerer that had killed many of the sorcerers from the golden age of jujutsu. After Sukuna had died, his fingers became cursed objects.

Fearsome Womb Arc
One of Sukuna's fingers was kept in an outdoor thermometer box at Sugisawa High School. The school's occult club had taken the finger from the thermometer box and had tried to remove the seal placed on it. Once they had taken the seal of the finger off, other cursed spirits that the finger had drawn in attack the club members. As Yuji Itadori and Megumi Fushiguro came in to save the club members, Yuji eats the finger in order to fight off the cursed spirits.

This causes Sukuna to be incarnated into Yuji, which he is excited about. As Sukuna plans to start a massacre, he is stopped by Yuji who reclaims his body, which surprises the cursed spirit that he is able to resist his control so easily. When Megumi plans to kill Yuji to exorcise Sukuna, Satoru Gojo shows up and decides to test out Yuji's will. Sukuna is then given control of Yuji's body and starts to attack Gojo, but Yuji manages to take back control after ten seconds.

The next day, another one of Sukuna's finger is shown to Yuji, with Gojo explaining how there are twenty of them and that they cannot be destroyed. Yuji then eats another of Sukuna's fingers and is able to still keep Sukuna under control. Days later when Yuji is brought to the Tokyo College, Sukuna finds out that Gojo is not the leader of the sorcerers and says how he is disappointed. Sukuna also tells Gojo that he will kill Gojo first when he takes over Yuji's body, for not killing Yuji right away. As Gojo says that it's an honor to be targeted by Sukuna, Gojo then explains who Sukuna is to a curious Yuji.

During an investigation at a detention center, Sukuna is forcefully given control of Yuji's body to combat a special grade cursed spirit before it kills them. Instead of taking on the spirit, Sukuna decides to fight with the spirit in order to take out Megumi. When the spirit starts to attack Sukuna, Sukuna easily blocks the attacks and easily overwhelms the spirit. Sukuna then decides to teach the spirit a lesson and uses his territorial expansion to easily cut the spirit into pieces. Sukuna then takes back his finger, which causes the spirit to die. Sukuna is prepared for Yuji to take back control, telling him to switch already, but when nothing happens, he eerily smiles realizing he can't.

Sukuna meets up with Megumi outside of the detention center, and removes Yuji's heart so that Yuji won't be able to switch with him. Sukuna then eats the finger that he had just got from the special grade cursed spirit and plans on killing Megumi. Sukuna and Megumi start to fight, where Sukuna easily defeats some of Megumi's shikigami, though he is impressed by the skill in which he utilizes them. Sukuna manages to push Megumi into a corner, questioning him on why he focused on fleeing, which confuses Megumi. Nonetheless, Megumi decides to fight seriously, which greatly enthuses Sukuna, but before the fight can continue, Yuji regains control from Sukuna, which results in Yuji's death.

After Yuji has died, Sukuna and Yuji start to fight one another within Sukuna's territory. Sukuna easily overpowers Yuji and after restraining Yuji, he tells him that they are not dead yet.

Sukuna proposes to bring Yuji back to life, with the condition that he will be able to take complete control of his body for a minute, but also swearing he won't harm any of his friends when he does. Yuji rejects and tells him just to revive him, so Sukuna proposes that they fight and the winner get their deal. Yuji accepts, but Sukuna immediately defeats him. Yuji is subsequently revived, aware that Sukuna is responsible, though with no memory of the deal he made with him.

Vs. Mahito Arc
One of Sukuna's fingers was placed in Junpei Yoshino's home, which resulted in Junpei's mother, Nagi's death. Mahito then shows Junpei the finger and explains how it draws in cursed spirits. Mahito also manages to convince Junpei that it was one of his classmates who was responsible, even through it was in fact Mahito and Geto.

When Junpei slowly dies from Mahito using his Idle Transfiguration on him, Yuji desperately asks Sukuna for help in saving Junpei, but Sukuna sadistically refuses and mocks Yuji for relying on him when things get tough. Sukuna and Mahito then laugh at Yuji for being unable to save Junpei from his cruel fate. This would result in an enraged Yuji trying to finish off Mahito to avenge Junpei's death.

During the fight, Mahito tries to attack Yuji with his Idle Transfiguration, but Sukuna appears, warning Mahito not to touch his soul again and forces the curse out of his territory. However, Mahito taps into Sukuna's again upon witnessing Yuji breaking into his domain to help Kento Nanami. Sukuna senses that Mahito has touched his soul again and brutally wounds him for attempting to mess with him. Sukuna's finger is then collected and brought back to the college.

Kyoto Goodwill Event Arc
The fingers that are at the Tokyo college are collected, along with the Death Painting Wombs 1-3, by Mahito.

Death Painting Arc
After Sukuna was incarnated, the finger at Yasohachi Bridge awakens and starts to kill people. Megumi manages to defeat the spirit that has Sukuna's finger and retrieve it, which Sukuna is glad that Megumi was able to get stronger. After Yuji and Nobara reunite with Megumi, Sukuna creates a mouth on Yuji's palm and eats the finger when Megumi gives it to Yuji.

Days later, Sukuna taunts Yuji about how his awakening is killing people because he had eaten one of his fingers, which Yuji simply tells Sukuna to not to tell Megumi.

Shibuya Incident Arc
As the Shibuya Incident occurs, Gojo is sealed in Prison Realm by Pseudo-Geto, and the next step for the cursed spirits is to deal with Yuji and Sukuna. Mahito and Choso want to kill Yuji for their own reasons, but Jogo wants to release Sukuna. They decide to make it a game to see who succeeds in their goal.

After Yuji's fight against Choso, Sukuna comments on how pathetic it was that Yuji could have lost to an inferior opponent, but is surprised when he suddenly stumbles away, sparing his life and leaving him unconscious.

Right after this, Suguru Geto's subordinates, Nanako and Mimiko Hasaba, approach Yuji and force feed him one of Sukuna's fingers they had collected. Jogo then appears behind them, scaring them away, and proceeding to force feed him the ten fingers they had collected, bringing the total Yuji has ingested to fifteen.

While Jogo still has his fingers around Yuji's neck, Sukuna takes control, demanding the cursed spirit to take them off. He commands the three to kneel before him, and cuts off the top of Jogo's head when he only takes a knee. Sukuna asks Nanako and Mimiko what they want with him, giving them one finger's worth of time. They ask him to kill the imposter possessing Geto, but he simply kills the both of them, as he doesn't like them ordering him around.

Sukuna then asks Jogo, but Jogo says that he wants nothing and explains how he just wants Sukuna to be fully revived. Jogo explains how Yuji can't take control right now and advises that Sukuna make a binding vow to permanently take control, but Sukuna rejects it since he has other plans. Sukuna then makes a deal with Jogo: if he can land a hit on him then he will kill everyone in Shibuya (minus one), which Jogo agrees to.

Sukuna then fights Jogo and completely overwhelms him. Sukuna taunts Jogo, while easily dodging all of his attacks. As Jogo uses his Maximum: Meteor attack, Sukuna notices several sorcerers and curse users on the ground preparing to flee. He suddenly appears before them and forces them all to stay put until he gives the signal. They all stand around fearing for their lives as the attack gets closer, before Sukuna eventually allows them to move right as the attack lands.

Jogo thinks he's succeeded, but Sukuna easily comes out of it unscathed. Sukuna wonders why Jogo is not using his domain, which Jogo says that his domain would lose. As things get interesting, Sukuna starts to use fire based attacks much to Jogo's confusion. Sukuna prepares to continue his fight with Jogo and subsequently defeats him.

As Jogo is dying, Sukuna meets with him and explains how Jogo is weak for trying to be like the humans. As Jogo agrees with him, Sukuna also explains how he had fun fighting Jogo and that he should be proud. Jogo starts to cry and wonders what it is, which Sukuna says that he doesn't know. Suddenly someone shows up to escort Sukuna, which he wonders who they are, only to recognize the person as Uraume. Suddenly, Sukuna senses that Megumi has summoned a powerful shikigami, and tells Uraume that he has something to do. Sukuna tells Uraume that it won't be long until he is completely free, and that Uraume shouldn't neglect their preparations; he bids them farewell and leaves.

Sukuna quickly arrives at the shikigami's location and saves the sorcerer that was facing off against Megumi. Sukuna notices the situation and thinks about how it was a good idea to save them since his death would result in Megumi's death as well. Sukuna heals Megumi and tells him to not die yet since there is something that he needs Megumi to do still. Sukuna thinks about how he'll defeat the shikigami, then that would void the ritual since he is an outsider. Sukuna then prepares to face the shikigami.

Mahoraga attacks with its sword, which Sukuna manages to block. Sukuna then wounds Mahoraga with his technique and figures that Mahoraga's sword is capable of exorcising any spirit since it uses positive energy. Mahoraga heals itself, which Sukuna attacks again but Mahoraga manages to counter it. Sukuna figures that Mahoraga is capable of seeing his technique. Mahoraga attacks which Sukuna tries to block but is sent flying. Mahoraga attacks again but Sukuna dodges and wounds Mahoraga.

Mahoraga heals itself again, which Sukuna figures that Mahoraga's ability is to adapt to any and all phenomena. Sukuna thinks about how this is what Megumi was trying to summon in their last fight, and that Mahoraga would have killed him. Sukuna then activates his domain: Malevolent Shrine, and uses its effect to cut up everything within a certain distance. While this is happening, Sukuna thinks about how to use his ability to defeat Mahoraga. When Mahoraga starts to heal, Sukuna uses a different ability to defeat Mahoraga.

Sukuna starts to leave, and tells Megumi's attacker to leave, in which the attacker runs into Sukuna's domain and dies. Realizing he's about to lose control of the body to Yuji, Sukuna quickly takes Megumi to get medical treatment and leaves. Returning back at the location where he had fought Mahoraga, Sukuna tells Yuji to take a look at all the destruction he caused, as Yuji takes back control, horrified by it all.