Japan's national health insurance system isn't perfect, but it's fairly airtight. Unless you have a condition that might benefit from some sort of experimental treatment which has yet to be approved by the government, everything is covered, meaning you won't pay more than 30 percent of the cost of that treatment. And if the amount you do pay exceeds a certain amount, the government will pay for most of that as well, so there is very little danger of, say, a patient having to mortgage his house to pay for care, even for a so-called catastrophic illness, which is something that occasionally happens in the United States.
But that doesn't mean there aren't medical situations where people end up paying a lot of money; it's just that they probably don't have to. This is why we've always been mystified by the supplemental health insurance business in Japan. Why buy extra insurance when the national system takes care of everything? One of the main reasons is private rooms, which the government doesn't pay for. National insurance covers overnight stays, but only for non-private rooms, and only a very limited amount. If a patient wants a private or semi-private room, or even a special type of bed in a non-private room, he or she has to pay for it out of pocket.
Some doctors use this exception to make money. An acquaintance of ours, whom we'll call A-san, recently told us a story about a visit she made to a private gynecology/obstetrics clinic in Saitama Prefecture. A-san was worried about her 77-year-old mother, who lives separately from her and has been suffering from a gynecological disorder for almost a year. Though she had been to her local hospital, the doctor there said he could not treat the condition properly, and while it wasn't life threatening, it made everyday life difficult. A-san's mother is on a fixed income and not tech-savvy, so A-san Googled the name of her condition and the first clinic that came up in the search said it had experience treating elderly women for that particular condition and happened to be not far from her mother's home. She made an appointment.