Out of all the Jujutsu Kaisen ideas I've planned, this one was the most updated, so I'll release this first. I WILL eventually release the others, but only once I've gotten at least 3 chapters on AO3. Please understand, and I do hope anyone who is a fan of Yuji being overpowered would enjoy this, along with hopefully the fact that Gojo will end up being more explored, culminating in what I can hopefully assure you will be pretty touching and nice, just like how Gojo told Yuji in the end of the manga that he wanted his friends and students to move forward without him.
"What do you want Yuji to do? He's not like us who you abandoned for 150 years? You must have a plan for him."
"... Ah. I don't really have a concrete plan for that thing. I guess if I had to say, then he's just a vessel. That role is finished now though. Itadori Yuji was merely the smoke signal that set things off. As long as that thing continues to coexist with Sukuna, the cycle of Curses will never end. He will become the eye of the storm for the new era."
That was all Kenjaku spoke to Choso about Yuji, clearly hiding the truth. However, what if Kenjaku decided to reveal exactly WHAT Yuji Itadori is at this moment? This is the beginning of Yuji Itadori becoming the new Strongest Sorcerer.
... Heh, out of all your brothers, you're the least failed one. So you've figured out I had something in mind for him, eh? Alright, let me tell you, since I'm also very interested in exactly what Yuji Itadori can do if he becomes aware of his true potential. He has the soul of Sukuna's twin, to put it simply.
!? Sukuna's twin!?
When Sukuna's mother was pregnant, she had twins, actually, but she was malnourished, and thus Sukuna was forced to consume his own brother in the womb to avoid starvation. That twin's soul bounced around aimlessly until I was able to find it. The man who inherited Sukuna's twin soul became the father of Yuji Itadori, and from there, I also sealed one of Sukuna's fingers inside him from the womb. Of course, once that man outlived his usefulness, I killed him and infused the soul of Sukuna's twin inside the boy. Thus, Yuji Itadori became the closest thing I currently have to being a... masterpiece.
So you killed Yuji's father!? Killing my mother wasn't enough, but you also had to kill Yuji's father as well!?
Ha, he was so eager to cast aside his wife when he found out she couldn't give him children. I granted him his wish and took his life in return. I must say, unlike your mother, at least HE lived up to my expectations. You could say he's the perfection you and your siblings were supposed to be. From having one of Sukuna's fingers sealed within his body, he was granted superior physical abilities that could match even that of Heavenly Restriction as his body was strengthened over and over again by the essence of a mighty Cursed Spirit, and then he also took in Sukuna's twin soul, thus gaining access to such potential for jujutsu as to be capable of rivaling and surpassing even Sukuna.
... Considering that you already decided to merge Tengen with the people of Japan, why the hell did you even brother to do something like that?
Why? Well, let's just say that the merger and Yuji Itadori are two different projects. I must say, Yuji Itadori definitely exceeded my expectations. I'll be looking forward to what he is capable of should he reach full maturity.
Like hell I'll let you have Yuji too, you piece of shit!
Choso exhaled deeply as he finished recounting the story of what Kenjaku had told him to Yuji and the rest of Jujutsu High. All of them were stunned beyond belief, with a fair share of them even giving Yuji sympathetic looks. Yuji had his fists clenched as he learned the truth of his nature. That's the truth, Yuji. You'll always be my brother, so you don't have to worry about me, but- How do you feel?
... So that means I can become stronger than Sukuna, right? Yuji said as he eyed Choso. You said Kenjaku believed I could surpass Sukuna. As Ieri-san said, I'm like a cursed item that was soaked in cursed energy known as Sukuna, so as long as I can kill him, I'll embrace my nature. Yuji said those words with a certain amount of heaviness as everyone there eyed him with concern. I'm going to train now. Kusakabe-san, Ui-Ui, please start the switching training-
Now this ain't nice, right? Yuji and everyone else turned towards the direction where they heard Satoru Gojo's voice as Satoru casually stepped inside. Having such a big revelation about one of my prized students without me there? Anyway, I've heard everything, so... After a while, I think I've came up with a way to ensure Yuji could reach his maximum potential by the time the big old Showdown begins...
And so it was that the road was set for Yuji Itadori to become the next Strongest Sorcerer In History, as he trains in ways that defy time and prepares himself, be it mentally, physically, or in terms of sorcery technique, for the great battle.
Hey, Yuji... Sorry, but looks like this is as far as I can be with you. You'll have to walk the rest of the road by yourself. Yuji merely stared at his teacher sorrowfully as Satoru Gojo eyed him with uncharacteristic solemn gentleness. He knew what had recently took place. Sukuna had blindsided Gojo-sensei and killed him with something that pierced through even the Infinity.
Don't be too sad, okay? Be strong and don't think of yourself as just a cog or anything like that. After all, from now on, you'll be the next Strongest Sorcerer. I've passed on everything I could have to you back when we trained for the month, and everyone else has helped too. Remember, Yuji, you're strong, not just in body and sorcery, but also in mind. It's sad that I couldn't watch over you until you fully reached your utmost height, but all those time I spent with you proved worth it.
I know, Gojo-sensei. I know. Yuji said softly as Gojo-sensei smiled warmly and gently patted him in the shoulder before he was replaced with Nanami. When I told you to take it from here, I really meant it, Yuji. It's not as though I was trying to make things easier for you before I died, but I really did have faith in you. You made my final moments a bit brighter. Yuji gave a small, solemn smile as Nanami smiled at him once more. It was a smile that was real, but also seemed sorrowful. Live long and well, make the Jujutsu World a better place, and then you can choose if you want to head north if you want to become someone new or south to return to who you used to be.
And then Nanami was replaced by Principal Yaga, who laid a heavy hand on his shoulder. No Jujutsu Sorcerer dies without regrets, but you can at least find a way to forgive yourself and not be defined by your regrets, Yuji. You're not a killer, nor just a cog. You are someone who wanted to be a hero, so be one. You've got what it takes now. Go for it, Yuji. We all have faith in you.
And with that, Yuji began to step out of this subconscious plane as he walked forward to face the battle ahead. Like Principal Yaga and Gojo-sensei had said, he wasn't right to think of himself as just a cog. He might not believe himself as worthy to be called a hero, but he could at least try his best. He felt resolve overtake his grief as he embraced all the memories he shared with Gojo-sensei and the others during the month before the showdown, extending beyond just months due to Gojo-sensei's training.
Don't forget Yuji... What I told you.
Yeah... I am your legacy, Gojo-sensei, and I'll do my best to live up to it.
In a flash, Yuji was into the battlefield of Shinjuku, ignoring the struggles of Kashimo Hajime against Sukuna's incarnated form, as he knelt before Gojo-sensei and attached his body back. He couldn't bring back his teacher, but he could at least fight and be the legacy Satoru Gojo wanted him to be. Yuji teleported Gojo-sensei's body away just as Sukuna had finally finished off the other ancient incarnated sorcerer.
Well, well, well... Look what we have here. Just what do you think you can do here, brat? All alone. Sukuna taunted as Yuji stood up slowly from the kneeling position, having sent away Gojo-sensei to be buried properly. Hmm? What's this? As Sukuna noticed the change in Yuji, Yuji turned back and faced Sukuna unflinchingly, his face cold and hard. He had wore a specialized combat outfit for this battle, an armor with several sheaths for Yuji to carry Cursed Objects in.
What I can do here? Simple. Kill you. That was all Yuji had to say as he drew a katana from one of the sheaths in his armor and swung swiftly at Sukuna, who parried the attack with Kamutoke, the force of their clash causing the sounds of a thunderclap to occur around Shinjuku.