Born in Owari Province in 1570, Mizuno Shigenaka had an audience with Tokugawa Ieyasu in 1576 and served as a close attendant with a stipend of 5,500 koku. He became a captain of the great guard in 1588 and served at the Battle of Sekigahara in 1600. In 1606 he was entrusted with guardianship of Ieyasu's tenth son, Tokugawa Yorinobu, and in 1608 became Yorinobu's chief retainer, granted 10,000 koku in Hitachi Province. He followed Yorinobu through his transfers to Sunpu and then Kishu domain; when Yorinobu became lord of Kishu in 1619, Shigenaka was granted 35,000 koku at Shingu and became lord of Shingu Castle as the domain's attached elder (tsuke-garo). He continued the castle construction begun by Asano Tadayoshi and assisted Yorinobu's administration of Kishu domain. He died in Wakayama in 1621 at age 52. His Mizuno descendants continued to hold Shingu Castle for generations, and after the Meiji Restoration in 1868 became independent lords of Shingu domain.

As guardian to the young Yorinobu and de facto administrator in his stead, he was a deeply trusted and loyal aide. He also demonstrated administrative skill in castle construction and the development of the castle town.

The Shingu Castle ruins are today designated a National Historic Site as "Shingu Castle Ruins and the Mizuno Family Graves," preserving the history of Mizuno rule at Shingu that began with Shigenaka.