Jigoku Sensei Nube: Gozen 0 Ji Nube Shisu!

Nube's class welcomes Jun, a withdrawn new student whose love of clowns hides a lonely life. His closest companion appears to be Pierre, a clown he sees in a mirror, but what seems like an imaginary friend becomes far more disturbing when Pierre gives Jun a strange mask with supernatural power.

Jun's behavior begins to change, and unexplained accidents spread through the school as midnight approaches. Nube senses that the mask is feeding something dangerous inside the boy. To save his student, the spirit teacher must uncover Pierre's true nature before the eerie game surrounding Jun claims a life.