Gakkou no Kaidan

Synopsis

Siblings Satsuki Miyanoshita and Keiichirou Miyanoshita move with their father Reiichirō Miyanoshita to their deceased mother Kayako's hometown. When their pet cat, Kaya, whom Keiichirou had taken to school hidden in his backpack, jumps out and runs into the old "haunted" school building, they decide to go in after him. There they meet Hajime Aoyama, Leo Kakinoki, and Momoko Koigakubo, and after running from several ghosts they meet Amanojaku. Amanojaku, a demon who feeds on children's fears, and as they become more scared, he grows larger and stronger. While trying to get away from Amonajaku, Satsuki finds an old diary which had belonged to her mother with notes on how to seal demons. The children exorcise Amonajaku, however, the camphor tree he should have been trapped inside had been chopped down, leaving him trapped inside Kaya.

(Source: Wikipedia)