Is Atom: The Beginning hentai?
No
Rated PG-13 (Teens 13 or older) on MyAnimeList and not tagged as Hentai.

TV · 2017 · 12 episodes · PG-13 - Teens 13 or older
Action, Sci-Fi, Seinen
Japan in the near future suffers an unexplained major disaster. Five years later, reconstruction is well underway. Two young researchers at a university are pinning all their hopes on robot development. Now their new interpretation of the eternal hero Astro Boy up until his birth is just about to start! (Source: Showgate)
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