Japan’s Softbank is to acquire smaller rival EMOBILE in a deal set to establish it as the country’s second-largest mobile operator behind NTT Docomo.

Softbank is to acquire JPY180.2 billion (US$2.3 billion) of stock in eAccess, the firm behind mobile broadband specialist EMOBILE.

According to Reuters, the JPY52,000 per share deal represents a premium of more than three times eAccess' closing price of JPY15,070 on Friday.

“We are paying more than triple the current trading price of eAccess because the benefits come from the company's existing customer base,” Softbank Mobile’s charismatic founder Masayoshi Son told reporters today. “We do not think our shareholders will view this as a bad tie-up at all."

It is estimating total synergies of JPY360 billion, made up of customer base expansion (JPY200 billion), network sharing (JPY110 billion) and “other management efficiencies” (JPY50 billion).

The deal will also see Softbank inherit valuable new spectrum to support both its 4G rollout and major new devices such as the iPhone 5.

It noted that the combination of EMOBILE’s 10,000 base stations at 1.7GHz with its existing 20,000 base stations at 2.1GHz would give it an estate of 30,000 “LTE base stations available for the iPhone 5.”

Softbank says it had 34.9 million subscribers at end-August, while EMOBILE had 4.2 million. The combination of the two would give the expanded firm 39.1 million – a 28.8 percent market share – enough to surpass KDDI on 35.9 million (26.5 percent). Market leader Docomo has 60.6 million subscribers, a 44.7 percent share.