More than 1000 passengers including foreign passengers in Diamond Princess Cruise Ship were released after their tests shown negative by last Friday. However, one woman’s test became positive on 22nd, Feb soon. This woman and her husband went back home on 19th, Feb. She had a fever of about 38.7 degrees from the 21st, Feb night. Pneumonia symptoms and virus test positive were confirmed on 22nd, Feb. 
By 2020/2/23 9:20 PM, there are 838 infections in Japan according to the NHK report. Diamond Princess Cruise ship passengers and crews are 691, which is more than 80% of total infections. Tokyo has 29 cases. Hokkaido has 26 cases. Osaka only reported 1 case. The others are shown in table 1.
It’s curious that Hokkaido infection number rise quickly in the recent several days. Hokkaido population density is lowest in Japan only 70 people/km^2. However, Tokyo is about 6015 people/km^2 and Osaka is about 4669 people/km^2. If Tokyo and Osaka numbers are correct, it means Tokyo and Osaka are under risk but still safe.
Some people doubt the number of authenticity in Tokyo and Osaka because their number is counter-intuitive. It’s very difficult to get the virus test if you don’t meet the condition defined by the Japanese government. Basically it depends on whether you have contact with people from China Hubei Provence, Zhejiang Provence, and other patients. If you only have a cough, you can’t get 2019-nCov virus test. Even if you want to pay by yourself, you just can’t do it. It almost means Japanese couldn’t get a virus test until they have severe pneumonia symptoms. However, the nfection will not stop when you don’t count it.