Los Angeles - Napster announced on Thursday that its Napster Mobile music service has launched with au/KDDI, the second-largest wireless carrier in Japan with over 20 million subscribers. Subscribers will pay about $3 a month for the service, plus additional fees for over-the-air downloads of full-length songs and ringtones. Napster said its mobile service is now available to over 60 million Japanese mobile subscribers, including through NTT DoCoMo's i-Mode.