Bicycle registration number
I was very surprised that bicycles are registered in Japan. I don't know if my bike has number... and I didn't register it. On of my friend got his bike stolen few months ago (while it was locked with a big lock), and he didn't even said it to the police cause it would have been useless. Policemen here are too busy ... showing themselves under the sun with their brand new expensives sunglasses and walking as sheriffs in any western spaghetti.
Here it is very close to Japan, because if a bike is stolen, it is obvious for everybody that it was stolen by a foreigner ... If you know what I mean.