The Classmate

Eun-Ha’s high-school life takes a dramatic turn when her bullies force her to perform a ghost-summoning ritual that brings Hae-Su, a charming yet unsettling spirit, into her life. Claiming to be her friend, Hae-Su starts exacting revenge on Eun-Ha’s tormentors. However, his violent methods concern Eun-Ha, and she begins searching for answers to uncover the past and his true identity.

(Source: WEBTOON)