I see a lot of job postings, for software developers, some different kinds of engineers and in the banking and finance industry. If you don't speak a lot of Japanese and are good-looking, you could also try modelling and acting. assuming your caucasian. Japanese love to have caucasian talent for their advertising campaigns.

I'd suggest you look for a multi-national corporation that has an office in both your home country and Japan. Perhaps then you could start off in your own country and then apply for a transfer. Speaking Japanese, will of course, help your chances.

I believe any college degree coupled with being a native English speaker will get you a full-time position. Having a college diploma will get you a part-time gig. My roommate was a part-timer at Nova and then he subsidized his income by selling bootleg dvd's to other teachers...smart chap.

Hope this helps and good luck.