Is Salaryman Kintarou hentai?
No
Rated R+ (Mild Nudity) on MyAnimeList and not tagged as Hentai.

TV · 2001 · 20 episodes · R+ - Mild Nudity
Action, Adult Cast, Comedy, Drama, Martial Arts, Seinen
The story follows Kintaro, former leader of a widely feared and respected biker gang, who decides that its time to "straighten out" and become a "salaryman" since his wife died and he has to take care of his young son. (Source: AniDB)
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