On this page
His family
According to the Japanese Wikipedia, Mutsu no Kami Yoshiyuki (1650–1710) was the second son of the smith Harima no Kami Yoshinari and the younger brother of Kōzuke no Kami Yoshikuni (上野守吉国, Kōzuke no Kami Yoshikuni). The same encyclopaedia gives two birthplaces: Nakamura, in Mutsu, now Sōma (Fukushima), or Sumiyoshi, in Settsu, now a district of Osaka.
Training
According to the Japanese Wikipedia, together with his father and his brother he learned in Osaka under the first Yamato no Kami Yoshimichi (大和守吉道, Yamato no Kami Yoshimichi). He was adopted by the Yamaoka family, and signed with that surname in Tosa.
In Tosa
In the Genroku era (1688–1704) the Tosa domain called him into its service, and there he was magistrate of the smiths (鍛冶奉行, kaji bugyō); that is why he is also called Tosa Yoshiyuki. Later he received the title of Mutsu no Kami, and he is said to have died in Osaka. Neither the year of his arrival in Tosa nor that of the title is recorded in a document of the domain among the sources consulted.
His brother Yoshikuni, known as “Tosa Yoshikuni”, appears in the wazamono list of the Yamada; Yoshiyuki does not.
Another blade in memory
The Japanese Wikipedia records another anecdote: Kōno Nagatoshi, first head of the balloon corps of the imperial army, gave a Yoshiyuki “inherited from the Tokugawa” to Tanakadate Aikitsu in gratitude for Yamada Isaburō’s balloon. Where that blade is now is not known.