Whispering Corridors: The Humming (2021)

Strange things happen in the closed toilets of Eunhee's old school, where she was deputy head girl. Hayeong and Soyeon, who used the place as their hideout, believed there was a ghost there after they heard a humming sound echoing in the toilet, even when no-one else was present. With a plant pot discovered by chance as evidence, Hayeong believes the mystery is linked to Eunhee, and after being accused, Eunhee suffers from visual and auditory hallucinations. She is also convinced that she was called there after seeing female students with injured faces all over her old school.