KDDI is Japan's second-largest telecommunications company, having successfully gained market share and profits against competitors since 2003, despite an initial resistance to smartphones. The company evolved from a former monopoly to a leading integrated telecom operator, with most of its revenue derived from mobile services under the 'au' brand, and is now transitioning to advanced technologies like LTE. KDDI also invests in new ventures, including mobile banking and Wimax services, contributing to its growth strategy and customer satisfaction efforts.