There was one theory that Nagayasu believed that Masamune was more fit to be the ruler of Japan than Ieyasu, and participated in the Masanune's plan to overthow the bakufu.
一説に長安は、家康より政宗のほうが天下人にふさわしいと考え、政宗の幕府転覆計画に賛同していたと言われている。