Softbank will pay 52,000 yen ($670) for every eAccess share under a share swap that will be completed in February, Softbank said after the market close on Monday, a premium of more than three times eAccess's closing price on Friday of 15,070 yen.

Shares of eAccess were untraded with a glut of buy orders. The stock was notionally quoted at 20,700 yen, up 9 percent from its Monday close of 19,000 yen.