Under the deal, SoftBank will buy 221 billion yen ($2 billion) of Yahoo Japan shares from Altaba, formerly internet giant Yahoo Inc. Yahoo Japan will then buy back 220 billion of stock from SoftBank.
As a result of the transaction SoftBank's stake in Yahoo Japan will rise to 48.17 percent from 42.95 percent with just a $9 million net investment. Altaba, Yahoo Japan's second largest shareholder, will have about 27 percent and end a joint venture partnership.
SoftBank said in a statement on Tuesday the deal will strengthen cooperation between the company, one of Japan's big three telecoms firms, and Yahoo Japan, an internet heavyweight in areas such as news and shopping.
The synergies between SoftBank and Yahoo Japan are "consistent with SoftBank Group's broader strategic synergy group initiative," SoftBank Chief Executive Masayoshi Son said in the statement.