Miyoshi Isan-nyuudō, also identified as Miyoshi Harumi Nyudo, bears the suffix "Nyudo" signifying his status as a Buddhist priest. He served the Tokugawa clan during the Keicho era, a period marked by their drive to consolidate control over Japan, culminating in events like the Battle of Sekigahara. As part of the Tokugawa faction, he participated in the confrontation at Ueda Castle where Tokugawa Hidetada sought the surrender of the defiant Sanada clan. The Sanada forces, under strategist Sanada Masayuki and his son Sanada Nobushige, resisted Tokugawa pressure. Miyoshi Isan-nyuudō's position placed him directly among those opposing the Sanada clan's stand during this conflict.