Japan Post Holdings Co, is planning to invest about $2.6bn in Aflac Inc, aiming to become the largest shareholder in the U.S. insurer. Japan Post, a conglomerate that spans postal delivery, banking and insurance services, plans to initially acquire a 7 to 8 percent stake in Aflac for about 300bn yen ($2.6bn). Under the deal Japan Post can increase its stake to a maximum 20% in four years time The transaction, which is expected to be announced this month, will follow the agreement made in 2013 between Japan Post and Aflac which allows Aflac to sell its cancer insurance at Japan Post’s offices across Japan.