Jujutsu Kaisen (Jujutsu Kaisen, Volume #0) by Gege Akutami
The prequel to the supernatural exorcist adventure Jujutsu Kaisen!
In a world where cursed spirits feed on unsuspecting humans, fragments of the legendary and feared demon Ryomen Sukuna were lost and scattered about. Should any demon consume Sukuna's body parts, the power they gain could destroy the world as we know it. Fortunately, there exists a mysterious school of Jujutsu Sorcerers who exist to protect the precarious existence of the living from the supernatural!
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 is noticed by Satoru Gojo, a teacher at Jujutsu High, a school where fledgling exorcists learn how to combat curses. Gojo convinces Yuta to enroll, but can he learn enough in time to confront the curse that haunts him?