What is a diploma candidate? Foreigners can't be hired unless they satisfy visa requirements.
You are married to a Japanese and have a spousal visa or permanent resident status.
You are not married to Japanese and you have a PR status.
You have a work visa, which usually means you have a 4-year college degree. (many years of related work experience can substitute for the degree)
You are a dependent of a Japanese and have a dependent visa.
You are on a working holiday visa. (this depends on your country and its arrangement with Japan)