The Tokyo and Osaka stock exchanges have agreed to merge in 2013 as they seek to strengthen their positions in a global market in the midst of a wave of consolidation.
Under the terms of the deal, the TSE will pay Y480,000 a share for its smaller rival, a 14% premium on Monday's closing price, creating a merged company tentatively called the Japan Exchange Group.
The Tokyo Stock Exchange accounts for around 90% of the country's equity trading while its Osaka rival has a strong hold on the domestic derivatives market.
In a statement, the pair say that they need to pool their resources to compete in a world where investors can trade where they want thanks to IT and telecommunications developments, choosing from a range of super-operators.
A merged player will create the third biggest exchange operator in the world and strengthen "competitiveness by such means as expanding its scale, diversifying the financial instruments in which it deals, and reducing costs".
These cost reductions include around Y7 billion a year in synergies thanks to systems integration. In March the TSE outlined plans for a major overhaul of its systems infrastructure, spending Y25.9 over the next three years.
Says the statement: "For a Japanese stock exchange to survive such global competition as a player, it must establish a highly liquid and efficient market and enhance the convenience of investors and companies through strengthening its competitiveness by such means as expanding its scale, diversifying the financial instruments in which it deals, and reducing costs."