Miyamoto Mikinosuke (宮本 三木之助, 1604 – 1626) was a retainer of the Japanese clan of Honda during the Edo period of Japan.
[a] Shimanosuke served Mizuno Katsunari, a near vassal of Tokugawa Ieyasu who was Musashi's commander during the siege of Osaka castle.
[2] It is almost certain that Shimanosuke died during the siege and it is likely that Musashi took custody of Mikinosuke as well as his younger brother Kurōtarō afterwards.
Afterwards it appears their adopted father brought them to Hirafuku, where Musashi's stepmother Yoshiko was living with her husband, Tasumi Masahisa.
Mikinosuke and another page named Iwahara Gyūnosuke helped Tadatoki's wife Senhime nurse their lord for several weeks while he became worse.
As tradition required, he performed the act in front of his master's grave on the sixth day following the latter's death.
Mikinosuke's grave is located at the Engyō temple, situated behind that of Honda Tadatoki and its inscription reads "Miyamoto Mikinosuke, adoptive son of Miyamoto Musashi: Having served Tadatoki and committed seppuku in front of his master's grave, a native of Ise, and adoptive son of Musashi, aged twenty-three."