Born in Aomori, Japan, Hideo, was a prolific Japanese writer who completed over 100 screenplays. He is best known for co-writing screenplays for a number of films directed by Kurosawa Akira, including Ikiru, The Seven Samurai, Throne of Blood and The Hidden Fortress. His first film with Kurosawa was Ikiru, and according to film professor Catherine Russell, it was Oguni who devised that film's two-part structure. Film critic Donald Richie regarded him as the "humanist" among Kurosawa's writers. In 2013, Oguni and frequent screenwriting collaborators Kurosawa, Hashimoto Shinobu and Kikushima Ryuzo were awarded the Jean Renoir Award by the Writers Guild of America West.

He was Akira Kurosawa most frequent screen-writing partner, having worked on 7 of Kurosawa's films. His specialty was in guiding the themes of the film and maintaining consistency throughout the script. Third collaborating writer, Shinobu Hashimoto, said that their writing process was that he (Hashimoto) and Kurosawa would write the script and hand the pages to Oguni, who would either nod his head yes or no and they would write accordingly (source: IMDb).

Writing credits other than for Kurosawa films include Gosho Heinosuke's Entotsu no Mieru Basho in 1953, Shima Koji's Warning from Space in 1956, Tora! Tora! Tora!, and Inagaki Hiroshi's Machibuse in 1970. (Source: Wikipedia)