The Market for Game Design jobs in Japan would be extremely competitive. The market for games is completely different over there as well compared to almost anywhere else in the world. I'm a gamer myself and was suprised by the amount of games only released in Japan, i knew they had alot of their own titles but seriously, the sheer amount is like wow!

And because of that, the market is a hell of alot more competitive. Western made games or companies like Microsoft's Xbox don't do well in the markets over there compared to the likes of Sony & Nintendo (home grown companies). Being in the shops, xbox sections only have a very very small area of the shops for their viewing selection of games while Nintendo and Sony made games and hardware completely fill the shops, alot of the titles i haven't even heard of them before. And from observation the majority of xbox games stocked were developed by homegrown companies such as Capcom/Konami etc

Not only would you have the competition of any Japanese trying to get into the profession but also any other foreigners who would be trying too also

If you are serious about it.... start learning and studying programming, 3d engines and designing and all the other related skills and start builing a portfolio. You will very most likely have to work to build yourself up at home with your own projects, be it by yourself as a Indie developer or working in a company. Getting more experience and building up more skills as because trying to even attempt to enter the market straight out of college with little to no experience or work you're just setting yourself to be shot down.

Just bear in mind that it will be a hard road and the good possibility it might never happen. Take some of the points into consideration and apply yourself to make video games because you enjoy doing it. Doing it because for another reason is only bad motivation and in the end the results won't equal the effort