Bicycles in Japan

In Japan everyone uses bicycles - jitensha, young and elders, women and men, school children and salarymen, mothers with small babies and policemen... Not even the bad weather would stop them, I've seen cyclists in heavy rain, dressed in sophisticated raincoats or with umbrellas mounted on bikes and I've seen them in scorching summer heat. Most of them are riding on the sidewalks and I admit that they manage to scare me sometimes... I rode bikes for many years, but I would not dare to ride on crowded sidewalks, like them...

Obviously, so many bikes must be stored somewhere, and I've seen huge bicycle parkings, some on multiple floors, near train stations, schools, office buildings and commercial areas. Many bikes are simple regular models, looking amazingly similar and every time I pass nearby a bicycle parking, I wonder: how do they manage to find their bikes?