The majority of Japanese wear masks to protect themselves from the growing pollution but there is an island in Japan where every individual wears gas masks all the time. Just an hour from Tokyo we can find Miyake Island. The whole population there is forced to wear gas masks.
The reason for using gas mask constantly is because there is an active volcano located on the island. With many explosions in the past, the surrounding has become very dangerous to walk without any protection. It is very dangerous to go outdoor as the poisonous gassed from magma is very harmful.
Now the island is actually a tourist destination in Japan. Many people are very much curious to see the place and the people living there in peace. And all the tourists are forced to wear a mask while they visit the island.