Sukuna Ryomen (両面宿儺 りょうめん すくな) was the evilest cursed king existed 1000 years ago. After he has incarnated into the body of Yuji Itadori in the present day, he is still cruel to everyone except for Megumi Fushiguro.
The scenes we can tell Sukuna is interested in Megumi
- Sukuna first met Megumi at the Eishu Juvenile Detention Center. At the time, he seemed he was surprised at Megumi’s Jujutsu technique. Later, he said about Megumi to Yuji that they could see something interesting soon.
- At the fight against Mahito in Junpei’s high school, there was the explanation that Sukuna didn’t care who died or not except for only person (Megumi).
- When Megumi once underwent asphyxia in the Shibuya incident, Sukuna came to heal him. At the time, Sukuna said to Megumi “Don’t die. There is something I want you to do.”
So, why is Megumi so special for Sukuna? Here is my consideration.
Megumi might be able to bring dead people back to life.
Technically, I should say his Jujutsu technique might have the power to revive dead people. With his Jujutsu technique, The Shadows Technique, you can manifest 10 kinds of Shikigami through the shadow and this is already explained in the story. But there might be more power hidden in the technique which Megumi even doesn’t know and the hint is where the author Gege Akutami sensei got the idea of the technique from.
The idea of the Shadow Technique is based on the Japanese historical document.
Gege sensei must have got the idea of the Shadow Technique form the “Tokusa no Kandakara” written in the Japanese historical document “Sendai Kuji Hongi (先代旧事本紀 せんだいくじほんぎ)”.
The reasons are:
- The Shadow Technique in Japanese is “Tokusa no Kage Houjtsu (十種影法術 とくさのかげほうじゅつ)” which directly means “ten kinds of shadow technique” and Tokusa no Kandakara (十種神宝 とくさのかんだから) means “Ten Shinto Treasures”. They both have “tokusa” which means “10 kinds” in the names.
- One of the treasures’ name is “Yatsuka no Tsurugi (八握剣 やつかのつるぎ) and the name is used for the strongest Shikigami of the Shadow technique “Eight-Handled Sword Divergent Sila Divine General Mahoraga (八握剣異戒神将魔虚羅 やつかのつるぎいかいしんしょうまこら).
- In the Tokusa no Norito (十種祓詞 とくさののりと), there is the line which goes “Furube Yurayura (布瑠部由良由良 ふるべゆらゆら) and this is the spelling to summon Mahoroga in Jujutsu Kaisen. *Norito is the words read by a priest in the Shinto purification.
source: Nishinomiya Shrine official site (in Japanese)
The power of the Ten Shinto Treasures

According to the “Tokusa no Norito”, By using ten treasures with the spelling, you can get an overwhelming power which even revives dead people.
Sukuna hasn’t get back to life perfectly, he just has incarnated into Yuji’s body.
Why does Sukuna need the power of the Shadow Technique? That’s because if Gege sensei got the idea of the Shadow technique from the Ten Shinto Treasure, the Jujutsu technique is very likely to have the same power as the Japanese ancient treasures.
He has been trapped inside Yuji”s body and can’t control the body as he wants. He must want to get out of the situation and be free. Therefore, he needs the power of reviving dead people.
How does Megumi get the power?
Since you have to use all 10 treasures to gain the power, I think Megumi must exorcise all 10 Shikigami (He has exorcised 5 out of 10 so far), too. Then he may be able to summon an extra Shikigami kind of existence or be able to combine 10 Shikigami to the special one.
For more details about Shikigami, see my articles "What’s the Divine dog? The Shadow Techinique Of Megumi Fushiguro 【Jujutsu Kaisen】"
The pact between Yuji and Sukuna
The reason I think something or someone appears after the Shadow Technique sorcerer exorcised all 10 Shikigami is the pact between Sukuna and Yuji.
When Yuji was once killed by Sukuna in Eishu Juvenile Detention Center, Yuji got to come back to life under the pact with Sukuna and the pact is,
1. Yuji has to give up his body to Sukuna for 1 minute when Sukuna says “Keikatsu (契闊 けいかつ)
2. Yuji has to for forget about it.
And, Sukuna also added the condition to persuade Yuji,
3. Sukuna won’t kill or hurt anybody for the minute.
The meaning of Keikatsu

Keikatsu means “not seeing someone for a long time” and when Sukuna offered Yuji to bring him back to life is that they would get to see something interesting (He mentioned Megumi).
So, I think Sukuna knew he could meet someone he once had met before, and he needs Megumi for that.
The reason Sukuna wanted Yuji to forget about “Keikatsu” is maybe he didn’t want to anyone to notice what he was on.
Didn’t anyone succeed in exorcising all Shikigami?

No. The shadow technique has been passed down among the Zenin clan and no one was able to exorcise Mahoroga so far. But, according to Gojo, the era of first head of the family was Edo (江戸 えど) or Keichou (慶長 けいちょう) which is 500 years ago and Sukuna lived 1000 years ago. So, I guess no one really knows the history of the Shadow Technique before it had passed down to the Zenin clan.
Jujutsu Kaisen is now on hiatus due to Gege sensei’s health reasons. I hope he rests well and gets better soon!