You even need a registration for your bike in Japan. As a foreigner you would be randomly pulled over to be checked. As for scooters, this is such a different way/level of experience than walking. They cant be compared. Personally I when using a scooter i’m more looking out for potholes than seeing anything of the city. Walking is so much slower and allows you to make meaningful connections also with the inhabitants of a place (even pickpockets ;)