[1] Hara was born in the town of Kiyama in Saga Prefecture and attended Tomeikan High School.
In 1999, his work Ousamatsu won the runner-up grand prize at the 40th Tetsuya Chiba Awards He was assigned to an editor at Young Magazine where several of his one-shot stories were published but were never brought up at serialization meetings.
During his time there, he gained experience on how teams worked as well as the difficulties encountered such as when his senior left the company and had to cover for him.
With only a few words from Inoue, Hara realized that his work up to then had more emphasis on story rather than illustrations and adjusted the art style of Kingdom.
Notable mangaka who participated included Inoue, Eiichiro Oda, Masashi Kishimoto and Hirohiko Araki.
[10] On August 15, 2019, Hara attended a roundtable discussion with Game of Thrones showrunners David Benioff and D. B. Weiss.
In the 2019 live action film of Kingdom, Hara insisted that Chengjiao draw inspiration from Joffrey Baratheon.