Hirata was born in Seoul, Korea, in 1927, into a wealthy family. He was educated at the prestigious Tokyo University's School of Interior Design. Before joining Shintoho as an assistant director (under his older brother, Yoshiki Onoda), Hirata moved into still photography, and eventually joined Toho in 1953, under the studio's "New Face" program, which would lead to his casting in Godzilla (although Hirata was originally intended for the part of Ogata, eventually played by another genre regular, Akira Takarada).
