While Hirata starred in many movies (including Hiroshi Inagaki's Samurai trilogy), he is most well known for his work in the kaiju genre, including such films as King Kong vs. Godzilla, The Mysterians, Godzilla vs. Mechagodzilla, Terror of Mechagodzilla, and his most famous role of Dr. Daisuke Serizawa, the brilliant but disturbed young scientist in the original Godzilla, released in 1954.

[1] Hirata was married to the popular actress Yoshiko Kuga[2] from 1961 until his death.

[2] 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).

Although Hirata earned lasting fame with his part in Godzilla, the role also typecast him, and the actor would go on to star in over 20 other sci-fi fantasy films for Toho (among them The H-Man, Gorath, and Prophecies of Nostradamus, as well as an important recurring role in the original Ultraman series.

The actor's association with the kaiju genre continued right until his death, as he helped announce the production of The Return of Godzilla at a Tokyo press conference, but unfortunately Hirata was too ill to appear in the film, and the part would eventually go to Yosuke Natsuki, who had appeared alongside Hirata in Ghidorah, the Three-Headed Monster in 1964.