The number of unique users in Japan surged from 521,000 in April 2009 to 7.52 million in March, a 15-fold increase, according to the technology ratings service Nielsen Online Japan, as quoted in this New York Times article.
Twitter is catching up to Japan’s biggest social networking site, Mixi, which had about 10.8 million unique users in March. A February analysis by Semiocast found 14% of all tweets per day worldwide are in Japanese.
According to Nielsen, the percentage of Japanese Internet users who have used Twitter is 12.3%, higher than the service’s reach of 10.2% in the U.S. It is also higher than Facebook’s reach in Japan, which is only has about 1.4 million users.
One factor cited in the New York Times article that is fueling Twitter’s growth in Japan is “the compact nature of the Japanese script, which means 140 characters allows for more substantial and complex posts. The word “internationalization,” for example, takes up just 3 characters in Japanese.”