With Japan targeted by an ever increasing flood of visitors, the plain form of Japanese is spreading as a more inclusive means of communication in situations ranging from disasters to tourism.

"Every language must be respected, and when we communicate with people who don't speak Japanese, responding in their native language should be a priority," said Akira Yoshikai, head of Yasashii Nihongo Tourism Kenkyukai, a group that promotes plain Japanese and its potential in tourism.

"But when it's not practical to do so at an individual level, plain Japanese could be another option," he said.