Nagamori served Toyotomi Hideyoshi in a largely administrative capacity, helping conduct land surveys in Ômi (1591), Awa (1593), and Hitachi (1595). In 1595 he was given the fief of Koriyama in Yamato province with an income of 200,000 koku and was named one of Hideyoshi's Five Commisioners (go bugyô,) whose responsibilities were centered on the administration of Kyoto. He sided with Ishida Mitsunari during the Sekigahara Campaign (1600) and was appointed rusui (Lord Lieutenant) of Osaka castle. After Mitsunari's defeat Nagamori was deprived of his Koriyama domain and ordered to pay heavy reparations. His son Moritsugu was one of the defenders of Osaka Castle (1614-1615) and as a result, Nagamori was made to commit suicide.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005