Hamamatsu Domain
Mizuno Tadakuni was the second son of Mizuno Tadaaki, the daimyō of Karatsu Domain. As his elder brother died at an early age, Tadakuni became heir in 1805 and was presented to "shōgun" Tokugawa Ienari and future "shōgun" Tokugawa Ieyoshi in a formal audience in 1807. In 1812, on the retirement of his father, he became head of the Mizuno clan and daimyō of Karatsu. He entered the service of the Tokugawa shogunate as a "Sōshaban" (Master of Ceremonies) at Edo Castle in 1816. However, faced with increasing difficulties over the policing of the foreign trade port of Nagasaki, in 1817, Tadakuni petitioned to be transferred from the Karatsu Domain to the much smaller Hamamatsu Domain in Tōtōmi Province. Although both domains were ranked officially at 70,000 "koku", Karatsu Domain had an effective income of 253,000 "koku" as opposed to only 153,000 "koku" for Hamamatsu. As a consequence, this transfer was met with outrage and disbelief by his senior retainers, resulting in the "seppuku" of his senior advisor, but Tadakuni would not be dissuaded. The same year, within the shogunal administration, he received the post of "Jisha-bugyō" (Commissioner of Shrine and Temples).