Yuji Itadori could still be the main character. He might have developed new and more powerful techniques in this fanfiction, and be the one leading the charge against new threats in the future of the Jujutsu world.
Yuji Itadori is a main character. He's a high - school student who becomes a vessel for a powerful curse. Megumi Fushiguro is another important one. He has unique jujutsu abilities. And Satoru Gojo, a very powerful jujutsu sorcerer, is also a main character.
There are several characters who died in Jujutsu Kaisen manga. Some of the notable ones include [mention specific characters if you have the knowledge].
The concept of sacrifice is also a major theme. Some characters have to make sacrifices in order to protect others or achieve their goals. For example, they might sacrifice their own safety or their personal desires. And power and its control is important too. Characters are constantly striving to gain more power to defeat stronger curses, but also need to learn how to control that power so it doesn't consume them.
The Jujutsu Kaisen manga is indeed ending. It's been a great run, but all good things must come to an end. The final chapters are bringing closure to the characters and story arcs.