Is Jigoku Sensei Nube hentai?
English title: Hell Teacher Nube
No
Rated PG-13 (Teens 13 or older) on MyAnimeList and not tagged as Hentai.

TV · 1996 · 49 episodes · PG-13 - Teens 13 or older
Comedy, Horror, Mythology, School, Shounen, Supernatural
Nube is a clumsy, easygoing, and very kind teacher, but he has a secret under his glove on the left hand. He has a monster hand, and he also has the ability to sense ghosts and evil spirits. So he protects his dear students from these evil spirits with his monster hand, proving to be very powerful. (Source: ANN)
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