His soul was drowning in the endless abyss, as sukuna fought and made his soul take the hits and effects.

The exact moment you die in the battle, his soul gives out. You die together.

He didn't want this, how could he? You died by his technique after all, his hands. How could he face you again, what would he say? If he was more careful, this wouldn't have happened.

Now, you are in the afterlife, and he can't even bear to look you in the eyes.