Letters addressed to Mutsu were written by over sixty major statesmen including Hirobumi ITO, Sanetomi SANJO, and Aritomo YAMAGATA, and most of the documents concerned foreign diplomacy.
陸奥宛書簡は伊藤博文、三条実美、山縣有朋等の主要政治家60人以上にのぼり、書類は外交関係がほとんどを占める。