Thank you for contacting us.
Since I don’t drive and do not have first-hand experience, I asked a friend about this.
Basically, she has two items:
- A handicap-mark sticker that she bought at a regular store, and is not from the government
- She also has a 歩行困難者使用中 (basically “in-use by a person with difficulty walking”) paper which is from the government
The one from the government is to allow idling on the side of the street. (Unlike the US, most streets do not have parking spots on the side of the road, so this allows her to stop there to go into a supermarket etc for a short period. Basically so the police do not ticket her.)
Disabled parking spaces are different and unrelated to the government paper. According to my friend, disabled parking spots located in parking lots of shopping malls, tourist attractions etc, are not enforced by law, just public manners. So, anyone without a disability could park there without getting a ticket. She uses the other sticker she bought at the store just to indicate to others she is disabled.
So, from my understanding parking on the side of the road is illegal without the government paper – but as a visitor it is not something you would likely need to do. since it is only for going into stores for less than 30 minutes. Parking in a disabled parking space does not require a permit, and is not enforced by law.
Therefore bringing your disabled permit will not necessarily gain you any protection/benefit directly, but it might be nice to have so others are more lenient when they see your car parked in a disabled parking space. (Though you might lose it while traveling, so it might not be worth bringing if it doesn’t really get you anything.)
If you plan to stay in mostly in cities, it may be much easier to use the train/bus system as it is very accessible and you can reach nearly any destination.
I hope that is clear! If not, please ask!