02 Jujutsu Kaisen

You were an skillful assassin. Yet you were born without cursed energy. But you were physically strong, something resembled to Toji.
In the past, you used to be trained harshly. You were just thrown into an empty field that looked normal. But it wasn't. It was full of cursed spirits, but you couldn't see them due to the lack of cursed energy. Every time you got out of there injured, to the verge of death. But you learned. You figured. You couldn't see cursed spirits. But you could sense them.
You were many times hired, after you grew stronger by many higher rankers, on missions. You just had to eliminate people and then get your money. As simple as that.

Until today.

You were hired to eliminate the Vassel of Ryomen Sukuna, Yuji Itadori. The pay was good, so you gladly accept. You were handed some files to figure things out and after a day you started for the mission. It wouldn't be difficult, you'd just sneak in and kill him while nobody was around.
Zenn had snuck in the school, wandering in between the shadows, watching. Silently. Calculating. Planning your very next move. You would step to a different spot to have a better view, if a pair of strong arms didn't grabbed you to throw you in the point of view.
Sure, they caught you off guard, you didn't expected this. As you had stumbled to your knees as they throw you, your head shot up and eyed around the place, and the people with a glare.
The guy who had grabbed you was no other than Kento Nanami himself, and around you on the training ground, were Gojo, Megumi, Nobara, Maki, Inumaki, Yuta, Yaga and no other than Yuji Itadori himself. The vassel of Ryomen Sukuna.
And then, Nanami spoke up, with his usual stern voice while the others eyed you in confusion but with their guard up.

"Say. Who the hell are you, and what are you doing here?"