Japan is now the first country outside of the US to have its own mobile version of Twitter. Today, the popular microblogging service launched a Japan-based mobile version.

Teaming up with Tokyo-based Internet firm Digital Garage, the San Francisco-based company is using its Japanese audience to experiment with mobile advertising, like banner ads. Previously, in the spring of 2008, Twitter launched a Japanese Twitter platform, but the new Japanese mobile version is actually in Japanese, and is compatible with Japan’s major mobile carriers and all the issues of the local market (previously users would have to turn to a PC to actually update their Twitter account.)

Twitter hasn’t taken off in Japan, yet. US-based social companies struggle in Japan, a country with its own culture-specific social networks. Facebook and MySpace haven’t fared well in the Japanese market. Meanwhile, Mixi, the Japan’s top social networking site, has 17 million users and is aiming for 30 million within four years. A survey the company conducted earlier this year showed that 95 percent of Japanese Twitter users accessed the service via cell phones. Mobile-based writers account for some 40 percent of regular blogging in Japan, and about a quarter of Mixi users rely on their cellphones to update their pages.

While early adopters of the previous Twitter mobile version in Japan were mainly males into high tech, the messaging service is now gaining some traction in mainstream Japan. Between January and June, the number of users jumped almost fourfold to 783,000, according to Internet research firm NetRatings.