I wouldn’t tell potential employers that you “love Japanese design”, even if you think you do. What is ‘Japanese design’? Do you mean Nendo and Muji, or Kawasaki Motorcycles and Hello Kitty? I think more specificity could help you target certain kinds of companies/firms, making your job search more clear for yourself and in a potential interview. A blanket statement like that sounds like a general stereotype.
I believe Japan’s job market is notoriously tough for foreigners to penetrate. Their economy is limping along and doesn’t have the vitality or workforce of previous decades. One way that people get in, is working for a multi-national company with large offices both in your home country as well in Japan.
When I was graduating from university I had an interview with Mitsubishi Electronics. It was kind of a disaster but a good learning experience (as most disasters are). They were dipping their toes into ‘multimedia’ (this was 1996) and were hiring native-English design students from the USA to work in their design offices somewhere outside of Tokyo. The job would have lasted two years and would also have included an intensive language course at Monterey to start. I didn’t prepare well, and my interview was at the end of the day with a pair of quite jet-lagged Japanese engineers (they flew me from NY to LA for the 1/2 hour chat). In retrospect I think that would have been a fantastic experience to work abroad.
I think you will need assistance in the form of headhunters, design placement agencies, and other recruiters in order to get a job there. As such it would help if you knew what areas/industries/practices you were more interested in, as that would help a recruiter to ‘sell’ your skills.