Season 1 - Remember, Hari

The story takes place in a high school. Hari attends a high school with her two friends, Ka Eun and Hyun Woo. Rumors are circulating that one of the students in the school, Park Joo Min, is possessed by a ghost. Although Hari is skeptical of the rumors, strange events start happening in the school. A guy named Kang Lim shows up and claims that Hari and he were friends. Who is this mysterious boy and are the rumors true?