Cigarette butts constitute a huge amount of the garbage that fills our streets, parks, and oceans, all over the world. Japan is no exception to this, as although there is a small amount of littering, cigarette butts are still a common site, especially in the shop and club-heavy downtown areas like Shibuya and Roppongi.
Managing your cigarette butts is the number one responsibility of a smoker, but if there is no trashcan in sight, many can just opt to litter the butt rather than hang on to it until it can be properly disposed of. That is why it is a common sight in Japan to see small portable ashtrays. With these, you can both smoke without leaving ash strewn about the ground where you smoke, and subsequently put your used cigarette butt in there to throw away later. They make portable ashtrays in various sizes, and some even small enough to fit on a keychain, or in your pocket.