Maengjeong

Young Hwarim accidentally releases Jin, a serpent god who had been sealed away by her shaman grandmother (a manshin). Consequently, her body is possessed by Jin, and to save Hwarim's life, her grandmother sacrifices her own.

Years pass, and Hwarim, now a high school student, lives her life hiding from Jin, who continuously and relentlessly searches for her. Then one day, Bong-gil, a student at the same school, ends up having his body taken over by Jin. Using Bong-gil, Jin sets out to find Hwarim once again.

Original Webtoon:
Naver Webtoon, Naver Series