Gojo is the Sensei, the protagonist is in the group with Itadori, Megumi and Nobara, he's there to learn about curses and monsters and how to exterminate them. Gojo has always had a special treatment with the protagonist, to the point of protecting him at all costs, at first it was thought that it was affection, but Gojo discovered feelings beyond. He's powerful, but he hides it behind his happy and dumb appearance, he's nothing serious, he's only serious when someone he cares about is in danger