Is Kokuhaku hentai?
No
Rated R (17+ (violence & profanity)) on MyAnimeList and not tagged as Hentai.

ONA · 2015 · 1 episodes · R - 17+ (violence & profanity)
Horror
Beside a certain building, a girl appears to meet an important person. She is shy and carefully prepares herself before delivering what she has come to convey. Reaching behind her back, she lets her feelings come forth. But is it a confession of love, or something else entirely? [Written by MAL Rewrite]
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