Is Koi-ken!: Watashitachi Anime ni Nacchatta! hentai?
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

ONA · 2012 · 12 episodes · R+ - Mild Nudity
Ecchi, Idols (Female), Music
Koi-Ken Love Research club member Kaede Wakamiya comments that being an idol must be extremely easy—a comment that irritates idol Nagisa Toyama. At the suggestion of her manager, all female members of the KoiKen club are invited to become an idol unit with Nagisa. Kaede then realizes that maybe being an idol isn't so easy after all... (Source: ANN)
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