Arata was born in Los Angeles, US, on 16 November 1996 and his father is actor Chiba Sonny. He learnt karate and apparatus gymnastics since he was a child and made his debut in the US as an actor before returning to Japan in 2014. He won the newcomer award in the 40th Nippon Academy Award for his performance in the two-part movie "Chihayafuru". Coincidentally, his new surname coincides with his role's name in the same movie (Wataya Arata) which led to fans speculating on the origin of the name.
Sources: Sanspo / Sponichi / Oricon