It is a major financial institution that started in 1875 as a postal savings system, and that still today continues to operate primarily out of post office branches.

[4] Throughout the vast majority of its history, Japan Post Bank had always been fully government owned and organizationally a part of the postal system.

[8] After World War II, in 1949 the postal savings system was relaunched under the newly formed Ministry of Posts and Telecommunications.

[10][11] This was during the Meiji era, when the Japanese government was focused on encouraging economic and military modernization and avoid foreign debt to remain independent during a period of Western colonialism.

[7] A particular concern was foreign debt, as observers in Japan saw indebtedness in countries like China and Egypt leading to their subordination to their creditors.

Finally, ¥6 billion of investments by the postal savings system in overseas colonial territories vanished as the government struggled to control the domestic economy.

[4] To promote savings which could be invested into rebuilding the economy, Japanese officials issued relentless statements advocating for austerity and instituted measures to restore confidence in the financial system.

[11][4] During the Allied Occupation of Japan, deposits into the postal savings system were allowed to be invested only in government and municipal bonds and private financial institutions were mainly responsible for issuing capital.

[5] In 2011, after the Great East Japan Earthquake, shares of the postal bank were once again permitted to be sold to help finance rebuilding after the disaster.

[2] The respective shares had decreased to 36% and 61.50% by end-March 2024, implying that the government held an economic interest of 22 percent in Japan Post Bank.

[2] In March 2021, Japan Post announced it would invest ¥150bn ($1.4bn) to acquire a 8.3 percent stake in Rakuten in order to create a partnership dealing in logistics, mobile and payments businesses.

[19] In 2019, an internal investigation revealed thousands of instances where investment products were sold improperly, with 90% of 230 directly managed Japan Post Bank outlets involved.