Just in case you needed to know. In your local area there is an office. It is called a ward office. Make sure that you go down there and ask about information and how to enrol in a health insurance system. They will issue you with a card. You can use this card in the hospital to get treatment and then pay on the spot.
The Immigration Bureau has recently announced that as of April 1, 2010 all those applicants for either a new visa or an extension of their existing visa will be required to present proof that they are enrolled in one of the government-managed health insurance systems.
There is a requirement that all residents of Japan to be enrolled in a government-managed health insurance system has existed for some time. However, the requirement for foreign nationals applying for a visa to provide proof of insurance represents a significant change to the Immigration Bureau’s policy.
I hope that this will help you.