Film is supposed to be a universal language, but the film business in any given country is usually run by the locals for the locals. The one great exception is Hollywood, which has been making films for the world since the silent days and is open to talent, preferably English speaking, from around the globe.
The Japanese film industry is not Hollywood; the big media companies that dominate it focus almost exclusively on the domestic market, with the foreign audience an afterthought. Japanese filmmakers occasionally venture abroad, but their stories typically center on Japanese characters, with the natives serving as a comic or exotic backdrop.
Even so, non-Japanese have long worked in and around the domestic film industry, with actor, subtitler and sales agent being common job descriptions. In recent decades, however, outlanders have found other ways into the business, while expanding formerly narrow job descriptions.