Son, chairman of internet and telecommunications firm Softbank, made headlines last year when his company bought an 80 percent stake in Sprint for $22 billion.
"A merger between Sprint and T-Mobile would put Softbank on the global stage, which is good for Japan," Glen Wood, head of sales global at Mitsubishi UFJ Morgan Stanley Securities told CNBC. "It allows a strong leader to emerge in Masayoshi Son, whether you like him or not."
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Son's deal-making strategy has made him Japan Inc.'s poster boy as more Japanese companies pursue overseas acquisitions amid historically high cash levels and the Bank of Japan's loose monetary policy.
Japan ranked fourth globally in cross-border M&A deals during the first-quarter, data from Thomson Reuters showed. The value of announced acquisitions rose nearly four-fold from a year ago to $20.23 billion.
"This [Sprint-T-mobile merger] is a classic Japanese strategy where you don't go after the leader, and you don't even go after second place. What you do is put the third and fourth place and together, you have a bigger army that can take on the head of the dragon. I'm not surprised to see Son make this run," said Keith Fitz-Gerald, chief investment strategist for Money Map Press.
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With a net worth of $19 billion, according to Forbes, Son has his fingers in many pies.
At a press conference on Thursday, Son introduced a human-like robot that will be used to staff SoftBank cellphone stores, making it the first Japanese mobile operator to enter the robotics business.
Dubbed "Pepper," the robot will go on sale to the general public next year for 198,000 yen, or around $1,900.
The company also plans to develop a household robot that can care for the elderly, according to the Nikkei newspaper, which would put it in competition with Honda Motor's personal "Asimo" robot.
Japan's robotics market is forecast to hit nearly $35 billion by 2020, according to a 2013 trade ministry report.
SoftBank also controls 34 percent of Alibaba, the Chinese e-commerce company that is expected to make the largest-ever technology debut on New York's stock exchange later this year. With Alibaba's value estimated around $150 to $250 billion, SoftBank's stake could easily top the $50 billion mark.
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"Son has done an excellent job, you can't ask for more from a Japanese CEO. Apart from invading the U.S. market, Son could very well take over the world," said Ben Collett, head of Asian Equities at Sunrise Brokers.