Is Onegai☆Twins: Natsu wa Owaranai hentai?
English title: Please Twins!: The Summer Never Ends
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

OVA · 2004 · 1 episodes · R+ - Mild Nudity
Comedy, Drama, Romance
Two weeks have passed since the dilemma between Maiku, Karen and Miina was resolved, but their lives are more hectic than ever. Karen has become possessed in her newly discovered brother and Miina is desperate for attention as well, which leaves little time for Maiku to concentrate on his work. Therefore he decides to head out in the woods and set up a camp, where he can be work in peace. But, as always, we have Morino who is up to no good. To make things a bit more interesting, she organizes a field trip to Maiku's camp site, and encourages everyone to make some good summer memories.
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