I'm not sure what the chances are of you getting a job in journalism in Japan are at this moment..., especially a job that simply offers you a working visa off the bat.
If your degree is simply equivocal to that of a native Japanese persons I'd say, not much chance... Simply due to cultural differences, and the heirarchy of work, and you haven't said if you can speak Japanese fluently (or if at all)... You're 17, so I don't know how much time you've spent with the language. Also, your age... It would probably be a good idea for you to work in journalism in the states first just to see if you like the job, rather than going to another country where the stakes are 10 fold... Japan isn't going anywhere.
One thing that you should know about Journalism in japan is that it is very free of criticism. It's very factual, I don't know what type of journalism you're wanting to do, but it wont be of the Bob Woodward variety, especially as a foreigner.
Secondly, there are only a selection of newspapers in Japan, the majority of them being read are the national newspapers, Asahi Shimbun essentially and others... There looks like a slection of somewhat sparse and varied regional papers, but nothing like the states & Canada.
I have heard of foreigners getting jobs as magazine editors in say an area that they were familiar with, art, fashion, etc etc... This was say, in the 1990s though.
Goodluck.