[3] Per Japanese census data,[4] the population of Kaizu peaked around the year 2000 and has declined steadily since.

A midden from Jōmon period was found in Kaizu, which includes sea shells, tools, and human remains.

Originally, levees were only on the upstream portion of the city, leaving the downstream side vulnerable to floods.

During the Edo period, most of the area was divided between Takasu Domain and tenryō territory under direct control of the Tokugawa shogunate.

During the early Meiji period, the foreign advisor Johannis de Rijke worked on improving flood control and man of the dikes in this area.

[5] Kaizu has a mayor-council form of government with a directly elected mayor and a unicameral city legislature of 15 members.

Agriculture is the mainstay of the local economy, with rice, wheat, soybeans, cucumbers, tomatoes and green pepper as the primary crops.