Depending on where in Europe you live, there are some countries wich can get a Working Holiday Visa to Japan wich will let you stay in the country for 1 year and you would be able to work.
The homepage says: Only for Working Holiday Makers from Australia, New Zealand, Canada, Korea, France, Germany, the U.K, Ireland and Denmark so if you have the passport of one of this countrys you can get the Visa. If not you will have to try another way.
Working Holiday / Japan Association for Working Holiday Makers