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 attacks the club members. As Yuji and Megumi came in to save the club members, Yuji eats the finger in order to fight off the cursed spirits.

This caused 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. 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 start 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, which Gojo explains how their are twenty of them and that they cannot be destroyed. Yuji then eat another of Sukuna's fingers and is able to keep Sukuna under control, afterwards he is able to check up on his friends. 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 kill 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 given control of Yuji's body to combat a special grade cursed spirit. 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 then tells Yuji to switch with him already but is glad when Yuji 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's. Sukuna manages to push Megumi into a corner due to which Megumi decides to fight seriously. Before the fight can continue, Yuji regain control from Sukuna which results in Yuji's death.

Cursed Training Arc
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 propose to brings Yuji back to life, with some conditions that mostly benefit Yuji, which Yuji rejects and tells Sukuna to revive him. Sukuna proposes that they fight and the winner get their deal, which Yuji accepts but Sukuna easily defeats Yuji. Despite winning against the boy, Sukuna revives Yuji for his own plans.

Vs. Mahito Arc
One of Sukuna's fingers was placed in Junpei'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 force Sukuna to switch with Yuji, Sukuna warns Mahito not to touch his soul 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 reunited 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
Sukuna was seen watching Yuji's fight against Choso, and comments about how Yuji could have lost to an inferior opponent.

Sukuna manages to take control of Yuji's body, after Nanako, Mimiko, and Jogo feed Yuji some of Sukuna's fingers. Sukuna has the three kneel before him, but cuts off the top of Jogo's head when he only takes a knee. Sukuna asks Nanako and Mimiko what they want with him, after which he proceeds to kill 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 want Sukuna to fully revive. Jogo explains how Yuji can't take control right now and advises that Sukuna make a bind vow to permanently take control, but Sukuna reject it since he has other plans. Sukuna then makes a deal with Jogo: if he can land a hit on him then he’ll do anything they want (for now), which Jogo agrees to.

Sukuna then fight Jogo and completely overwhelms him. Sukuna taunts Jogo, while easily dodging all of his attacks. As Jogo uses his Maximum: Meteor attack, Sukuna forces the humans to stay put until he gives the signal. As the attack lands, Sukuna easily comes out 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 escorts Sukuna, which Sukuna wonders who they are but realizes that the person is 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. Sukune then bids Uraume farewell and leave.

Sukuna quickly arrives at the shikigami's location and save the sorcerer that was facing off against Megumi. Sukuna notices the situation and thinks about how it was a good idea to save the sorcerer 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 need 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. Sukuna then takes Megumi to get medical treatment and leaves while thinking about how it’s not much longer. Sukuna then arrives back at the location where he had fought Mahoraga, and tells Yuji to take a look as Yuji takes back control.