Japan has the original umbrella sharing economy. All umbrellas look the same (black handle, white or transparent top), are very cheap (a few hundred yen = a few dollars at any convenience store) - as a result, people aren't attached to theirs. Leave yours at the door when you enter a store or some such, take one when you leave - it might be yours or not. If it's not raining anymore when you leave, just leave it there.
It's wonderful - I've had many nights leaving a bar late when it was pouring and hadn't brought an umbrella with me, and the empty bar had a half dozen available by the door.
Turns out that it's very rare that you arrive with one, need one when you leave, and can't find one.