徳川家治
In 1778, the four-year-old Hitotsubashi Toyochiyo (豊千代), a minor figure in the Tokugawa clan hierarchy, was betrothed to Shimazu Shigehime or Tadakohime, the four-year-old daughter of Shimazu Shigehide, the "tozama daimyō" of Satsuma Domain on the island of Kyūshū. The significance of this alliance was dramatically enhanced when, in 1781, the young Toyochiyo was adopted by the childless shōgun, Tokugawa Ieharu. This meant that when Toyochiyo became Shōgun Ienari in 1786, Shigehide was set to become the father-in-law of the shōgun. The marriage was completed in 1789, after which Tadako became formally known as "Midaidokoro" Sadako, or "first wife" Sadako. Protocol required that she be adopted into a court family, and the Konoe family agreed to take her in but this was a mere formality.