Is Fushigi no Kuni no Miyuki-chan hentai?
English title: Miyuki-chan in Wonderland
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

OVA · 1995 · 2 episodes · R+ - Mild Nudity
Comedy, Ecchi, Fantasy, Girls Love
Rushing to school after oversleeping, Miyuki finds herself falling into a pit. When she regains consciousness, it does not take long for her to realize that she has entered another world as she begins to encounter different peculiarities and odd female figures, all wanting her to themselves. If Miyuki wants to go back to school, she must escape the bizarre situations and find a way to return to reality. [Written by MAL Rewrite]
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