In an exclusive French Interview from 2020, Jujutsu Kaisen author Gege Akutami confirmed that Sukuna And Yuji will never be allies.
According to him, Yuji’s relationship with Sukuna will not mirror the classic shounen trope where the main character befriends an alien entity inside them. Akutami gave the example of Naruto, where the protagonist could come to terms with the entity (Nine-Tails) inside of him.
However, sadly for Jujutsu Kaisen fans, Akutami thinks it’s not possible because Sukuna will never accept Yuji or the concept of love.
GEGE INTERVIEW FROM 2020 (Part-4)
Gege talks about Sukuna & Mahito. He says unlike Naruto where the villian (obito) ended up being accepted, it won't be the same for either Sukuna or Mahito. They are sinners who cannot be atoned.
(From a French Exclusive Interview) pic.twitter.com/HmXdq2onXF
— Myamura (@king_jin_woo) January 3, 2023
Further, he uses Mahito as an example, to state that Sukuna and Mahito are irredeemable. This is because Mahito is intrinsically evil and only thinks about making humans suffer, rather than being a goody-good character at heart.
To the mangaka, it was essential to avoid the “but deep down, he is nice” gimmick that shounen stories often employ. Gege went on to explain that he couldn’t hate Thanos at the end of Avengers, but that is not the case with JJK’s antagonists.