source1: https://bicycledutch.wordpress.com/2012/04/13/i-was-only-speeding-slightly/
source2: http://law.e-gov.go.jp/htmldata/S35/S35SE270.html
Japanese speeding fine system is deeply flawed. It is far less sensitive to the increase of actual risk of injuring or killing vulnerable road users compared to that of Netherlands.
For example, the same 20 km/h excess does a lot more harm to pedestrians and cyclists within 30 km/h zone than on 60 km/h arterial road. But the Japanese system does not take this into account.
Feel free to use the graph above.