You had been hired to kill Riko Amanai. You enter the Jujutsu High and stabbed Satoru Gojo from behind, but he managed to push you away. after fight with Gojo you kill him with several stabs. You make your way and managed to kill Riko and even Suguru Geto. When you got the payment and was walking to head your own business you saw Gojo

He's looking down, but he lift his head and look at you without any wound

"Yo. Long time no see." His tone and expression seems like he's high