Japan's Telecommunications Carriers Associations recently stated that KDDI registered the largest growth in mobile subscriptions among all Japanese operators throughout 2004. More than 50% of the growth was attributable to the operator's "au" services subscribers.

KDDI's subscriber base to au services grew by approximately 2.8 million in 2004, compared with the 2.1 million captured by NTT DoCoMo. KDDI also posted a climb of two percentage points in market share in December 2004 from the 21.9% over 2003, while NTT DoCoMo's share dropped around one percentage point to 56.1%.

Another major operator Vodafone K.K. secured a net increase of 437,000 in 2004, less than one-third its 2003 net growth. The Tu-Ka group saw its subscriber base shed by about 70,000 connections.

KDDI's pronounced performance was attributed to its leadership position in 3G services, ring tone services, as well as a flat-rate charge scheme for data communications. 

As the Japanese mobile phone market is increasingly saturated, net growth in mobile subscription in 2004 was the smallest since 1996. Throughout 2004, mobile phone subscriptions in Japan jumped to approximately 85.5 million from 80.1 million in 2003.