The short answer is, we don't know. There just isn't data to tell.
That being said, not that much testing has been made. The culture doesn't promote not downplaying or hiding your symptoms. Past couple of weeks, people have been relaxing. Cherry trees are in full bloom and so are the park gatherings. At the airport there are fingerprint scanners at the passport control - no way to sanitize your hands until after luggage unless you brought hand sanitizer. I could go on.
Tokyo's governor just mentioned the possibility of a Europe/China style lockdown: https://www.reuters.com/article/us-health-coronavirus-tokyo-...
Tokyo just picked up the rate significantly: https://www.mhlw.go.jp/content/10900000/000612031.pdf
CDC just raised Japan's alert rate: https://wwwnc.cdc.gov/travel/notices/warning/coronavirus-jap...
Internally, there are recommendations, and not much more. Bars and clubs are still going. Many offices are business as usual, apart from not demanding everyone in at 8:40 sharp to spread out commutes a bit more. Many of those expect to be able to return to that by April. (Just anecdata, my girlfriend happens to work at one such company)
Golden Week is coming up. For those who don't know, generally in Japan people only have around 10 holidays - but on the other hand there are a lot of holidays. It just so happens that in may several of those fall together and it's the one week every year where everyone goes traveling (there is also New Year's which is more focused on family).
I am not optimistic.