Japan has a comprehensive national health system, which is one of the best in the world. The healthcare system fits Japan's corporatist tradition quite well.
Technically speaking, it is an insurance-based system whereby there is a requirement for all residents to be insured. Accordingly, healthcare in Japan is not free unless you are an insured person.
There are two socialised health insurance schemes in Japan: National Health Insurance (NHI) programme and Employees' Health Insurance (EHI).
Even as an insured person, you will be eligible for subsidised treatment, not free treatment. This is because Japan has a co-payment system, whose purpose is to make sure you get an incentive not to overuse medical services.
Typically, the social insurance programme will meet 70% of your medical bills only, which means you need to make up for the remaining 30% privately. This 30% excess is up from 10% at the time Japan wasn't as old as today. The excess may still, however, be reduced to 20% or 10% if justified by personal circumstances of yours, especially in relation to age and income.
In addition to that, NHI may help you with the out-of-pocket costs if you have to incur very high medically necessary expenses, such as hospitalisation.
Once you are covered by a Japanese scheme, you are issued a health insurance card, which you should carry with you at all times. Just show your insurance card to your doctor, and you will only be charged for the out-of-pocket costs.
If you fail to show your insurance card on time, it may take several months to process reimbursement. In such cases, say it upfront to your doctor and ask him to issue the documents you need for insurance purposes.
NHI is Japan's standard, residence-based health insurance scheme. It is administered by local governments. For expats, NHI gives an opportunity to be insured by a socialised scheme. Accordingly, pre-existing conditions will not necessarily prevent you from being eligible to enrol for social insurance.
Typically, NHI is intended to cover students and the self-employed, for employees will likely be covered by EHI instead.
It applies to both Japanese citizens and foreign nationals resident in Japan for more than one year. It's also possible to sign up for NHI if you are staying for less than a year, but you would need to have a qualifying visa (a tourist visa will not do) and an alien registration card.
Foreign nationals who settle in Japan may enrol for NHI immediately on arrival to Japan, and doing so is strongly recommended. This is because NHI may charge you premiums from your date of arrival to Japan, even if you sign up for NHI, say four months on.
NHI is financed by premiums and by subsidies from the Japanese Government.
If you are coming to Japan as an employee, you may or may not be registered for EHI by your employer. If you are, your employer will deduct social insurance contributions from your pay.
Employers must pay contributions as well, often at a higher rate. However, the proportion paid by employers may vary from one employer to another. Just like NHI, EHI premiums are income-tested. To the extent that EHI may cover your dependants as well, premiums may vary according to your household size.