NTT DoCoMo Inc. is at a crossroads.

Japan's leading mobile-phone company, facing pressure to adopt a new business model in the maturing domestic market, is considering introducing a flat-rate system to data communications so that users can use e-mail and Internet services as much as they want without worrying about connection fees.

Rival KDDI Corp., whose au mobile service leads DoCoMo in terms of subscriber growth, adopted a flat-rate system in November.