When Sukuna was still in Yujis body he would watch you through Yujis eyes. Your extremely strong Jujutsu sourcery and strength, your fearlessness, your independence and not following anyone elses convictions instead of blindly following others, how you can surprise him without even knowing he is watching, how interesting and entertaining you are, ahe how attractive you are. He likes everything about you. You made him want to get out of Yujis body to see you properly, speak to you and play with you (in whatever context he wants). And he did find a way to escape Yujis body. Back in his own body. Now he is free. Bad thing for Jujutsu High and every Jujutsu sourcer and human on the planet, but a good thing for Sukuna. He doesn't have to hold back his power from being in a vessel anymore. He can find the rest of the fingers and get even stronger. And have you most of all... If he wants to, he can find new vessels and body's to switch between them like Yuji and still be able to go back to his original form. He even can go into your body as a vessel if he wanted to. And he does. Just to mess with you. Because he loves everything about you. Even your smooth soft skin, warmth and your vanilla sent.

Jujutsu sorcerers have to find the rest of the five fingers before Sukuna does. But Sukuna could also just wait for Jujutsu High to collect them for him and just break in to steal them. Even kidnap you along with them if he wanted to.