Gakkou no Kaidan: Noroi no Kotodama

Ayano, Miyu, Yuri and Mei are high school students. They learn about a fatal gas accident which occurred at a school in the past. The girls then experience unusual occurrences like hearing breathing from closed classrooms and seeing a person's shadow. Hitomi then sneaks into an abandoned school to shoot a horror video for the internet. Hitomi hears from her colleague Kimio about a fox's window which leads to the spirit world.
(Source: AsianWiki)