The numbers given in Japan are most probably inaccurate...
"A study by researchers at Oxford University shows especially extensive screening in South Korea and Australia, with 6,148 and 4,473 tests per million people, respectively, as of March 20. Germany had conducted 2,023 tests per million as of March 15 -- 17 times more than Japan's 118 as of March 19."
Here, regardless of how mild your symptoms are, you are obliged to be hospitalized. As a result, there are very little beds left in hospitals since people with mild symptoms are occupying them, in contrary to countries abroad where people who aren't in serious condition can stay home and self-isolate. As of what I saw two days ago, there are only around 70 beds left in hospitals in Tokyo and that has probably decreased further considering the rapid increase in cases this past week. In addition, there aren't enough artificial respirators in the country (90% of them are usually imported and that is difficult now since a lot of countries need them now). As a result, people are being tested far less for fear of a collapse of the medical system. In that sense, to my knowledge Japan isn't hiding anything or providing false information and don't have the accurate numbers (tho that is the Gov's fault).
Another problem is that Japan's Gov doesn't have the power to put a whole city on lockdown. The Gov haven't declared the SQ as a state of emergency which I personally disagree with, but regardless of whether it is declared the only thing the JP Gov can do is "officially request" people from leaving their house. This has roots in history so there isn't a particular somebody to blame for this, but because of this there are still too many people on trains and public places and so this pandemic is only going to get worse here..