Is Yozakura Quartet: Tsuki ni Naku hentai?
No
Rated PG-13 (Teens 13 or older) on MyAnimeList and not tagged as Hentai.

OVA · 2013 · 3 episodes · PG-13 - Teens 13 or older
Action, Comedy, Fantasy, Mythology, Shounen, Urban Fantasy
"Tsuki ni Naku" will take the story content from volume 11 of the manga, which features a visit to a onsen by the members of the Hiizumi Life Councelling Office, while the town's police force have to deal with a new youkai-hunter threat. This OVA is bundled with the limited edition of the manga (14th, 15th, and 16th).
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