Prior to entering the mobile market, Softbank employed a similar strategy in fixed-line Internet, undercutting rivals and waging aggressive campaigns with piles of free modems for new subscribers in front of busy stations. In addition to its mobile and fixed-line Internet firms, the company runs host of Internet properties including Yahoo Japan, Ustream, and a major investment website -- and its own baseball team.
If it successfully acquires Sprint, the newly combined company will gain much more leverage when making purchases from handset makers and the companies that make cellular equipment, as both Sprint and Softbank continue to roll out their next-generation LTE networks.
"The company should be able to get lower prices, and offer more savings to customers," said Amano.
Softbank also has a knack for oddball products that capture the imagine. Earlier this year, in the wake of Japan's nuclear disaster, it announced a phone with a built-in radiation detector. In 2007 it secured a deal with Walt Disney Japan and started its Disney Mobile service, which still offers Mickey-branded handsets with special wallpaper and icons.
The company's years of experience in the Japanese market could also help it introduce new technologies in the U.S. One example is NFC (near field communication) touch-card technology, which has long come as standard on mobile phones in Japan, said MM Research's Yokoya.
"NFC is starting to take off in the U.S. Softbank has lots of experience in this area," he said.
U.S. mobile operator Sprint and Softbank have said they are in negotations for Softbank to make a possibly "substantial investment" in Sprint, and news reports have said Softbank may then try to use Sprint to go after MetroPCS.
Earlier this month, Softbank announced it had sealed a blockbuster deal to acquire smaller domestic rival eAccess to help expand its mobile data network.