Jujutsu Kaisen manga volume 0 features story and art by Gege Akutami.

Yuta Okkotsu is a nervous high school student who is suffering from a serious problem...his childhood friend Rika has turned into a curse and won't leave him alone. Since Rika is no ordinary curse, his plight gets noticed by Satoru Gojo, a teacher at Jujutsu High, a school where exorcists are taught to combat curses. Gojo convinces him to enroll, but can Yuta learn enough in time to confront the curse that haunts him?