Hell Teacher: Jigoku Sensei Nube

Season 1, Episode 3: The Midnight Honor Student

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An unsettling shadow appears in the school in the dead of night. It's rumored that an honor student is erasing blackboards, replacing flowers of flower vases, and cleaning the rabbit cages when there should be no one there. To get to the truth of the matter, Hiroshi and his friends sneak into the school, only to encounter a voice in the dark saying, "Let's be friends!"