When Ieyasu was appointed Shogun on February 12, 1603, Nagayasu was given the rank of Junior Fifth Rank, Lower Grade and assigned to the governor of Iwami and also assigned to the attendant chief retainer of the sixth son of Ieyasu, Tadateru MATSUDAIRA.
1603年2月12日、家康が将軍に任命されると、長安も特別に従五位下、石見守に叙任され、家康の六男・松平忠輝の附家老に任じられた。