We've been discussing these questions recently on the #covid19 channel of the HN Tokyo Slack [0] - all the same sort of points raised as below - but nobody knows for sure.

There was an outbreak in Hokkaido a few weeks ago and that was the Japan hotspot for a while. The governor there quickly declared a state of emergency and that was brought under control - if you believe the official figures that is.

The best Japan tracker that I've seen is here [1]. From that you can see that there have been 16 deaths in 愛知 (Aiichi - prefecture capital is Nagoya) but only 141 cases as of now. Assuming deaths have an approximately average lag of 3 weeks from infection and an about 1% death rate, 16 deaths would translate to very approximately 1,600 deaths 3 weeks ago. As the general Japan is upwards, even according to official figures, there are probably several thousand cases in Aiichi today.

For new cases, in the last few days Tokyo is ahead.

Also, the government has given schools to reopen in April [2] . If that happens, cases may start rising sharply.

[0] http://hntokyo.io/

[1] https://covid-2019.live/

[2] https://www.japantimes.co.jp/news/2020/03/20/national/school...