Kazumasa Hirai (?? ??, Hirai Kazumasa, May 13, 1938 – January 17, 2015) was a Japanese novelist and science fiction writer from Yokosuka, Kanagawa.
He graduated from Yokosuka Industrial High School and the law department of Chuo University.
Hirai is well known for his SF-manga work.
He is the creator of 8 Man (aka 8th Man in the USA) and was well known as the story creator of the 1960s manga series "Genma Taisen" (Genma Wars) about a hero with psychokinetic powers and his battle against a space villain called Genma.
Hirai wrote stories for the Wolf Guy comic series, and also published comics co-authored with cartoonist Shotaro Ishinomori that were later adapted into an animated film in 1983.