Do you know the free magazine "metropolis"? ( http://metropolis.co.jp/ )
There are some job informations. I don't know if there are chef jobs.
Or how about asking directly to restaurants in Japan?
You may be able to start as a garccone...
Have you trained at Le Cordon Bleu or some other famous school? That would go to assisting you in getting a job and a visa, otherwise you are just a cook and to be honest, it will be very difficult for you to get a visa. Good luck!!!