Sadao Yamanaka has been called Japan's Phantom Genius of Film. Most of his movies have been lost, including all of his numerous silent films. At a time when Japanese ultranationalism was growing, Yamanaka, along with Daisuke Ito, popularized a subgenre of movies called tendency films that depicted the plight of the poor with unprecedented realism. Like Ito, Yamanaka stripped away the clichés of the samurai film and he laid the groundwork for the mature period film (jidai-geki) by subordinating plot to the subtleties of human emotions and the spirit of a film's period. Without Yamanaka, it is difficult to imagine the humanistic samurai epics of Akira Kurosawa and Masaki Kobayashi.
Yamanaka entered the film industry in 1927, when his schoolmate, the son of early film mogul Shozo Makino, helped him get a job in the script department of Makino Film Productions. Since his real ambition was to direct, he soon entered the directing department at rival studio Arashi Kanjuro Productions. His debut film, Dakine no Nagadosu, was ranked in the prestigious film journal Kinema Jumpo's annual Top Ten list. During Yamanaka's all-too-brief career from 1932 to 1937, he directed no less than eight films that placed on that coveted list. His final movie, Ninjo Kami Fusen, was widely hailed as one of the best films Japan had ever produced. This dark film concerns a samurai too poor to live with dignity or to die with honor. In 1937, when Japan was committing atrocities in Shanghai and Nanjing, and people suspected of communist or liberal inclinations were being openly jailed, this was a brave film to make. Yamanaka was drafted and sent to China as a common foot soldier. He died there, on September 17, 1938, at the age of 29.