[SSJup81]

By high level of proficiency, I was thinking along the lines of taking and passing the level 1 JPLT.

That aside, for foreigners, the only jobs I can think of is the generic English teacher job. Outside of that, if you work in an office that might work with a sister company in Japan and need a representative to work at the sister company, you can probably be a translator or liaison, or something like that.

Before actually deciding right off the bat to live in Japan, like others here, who are experienced, you should probably live there short-term to even see if you like it enough to want to live there long-term. That's why I want to do the JET programme and hope I can get in for next year. At least I'll see what it's like to work in the country and the atmosphere. If I like it enough, maybe I'll try pursuing a career there, but for now, short-term works.