IT is a good business to get into. If you can speak Japanese (I didn't read your post well enough to know, sorry ^_^
you'll be in for sure, or even if you can speak English and some other language.
One of my friends is making buckets of money in an international trading business but he can speak Spanish, English, Chinese and Japanese with fair fluency in all.
Getting a Job as an English teacher wouldn't be bad for you to test the waters here. See if you can get used to being in a different country before you really make the leap and come for a career.
I wouldn't recommend JET if you're uncertain about what you want to do here. They have a one year contract that you really can't break (You can but it's more disgraceful for them and harder on the school) At certain Eikaiwas it's usually expected that at the 6 month hump most of their new trainee's will bail. At BunnyCo. (*WINK*) i was told something like 20% of all new people will not even show up at training. Using the company to only get a work visa so they can work elsewhere.
Keep your eyes open, check out jobs and what will sponsor a visa, ask questions and good luck