He died alongside his brother as part of the Battle of Minatogawa on July 5, 1336.
Masasue fought alongside his Masahige throughout the Kenmu campaigns, including at the sieges of Akasaka and Chihaya castles, but other than his name, almost nothing is recorded about him in historical chronicles until his death at the Battle of Minatogawa.
[1][2] According to the war chronicle Taiheki, just before their deaths, Masashige turned to Masasue and said, "It is said that one's last thought in this life determines the goodness or evil of one's next incarnation.
To which Masasue laughed and replied, "It is my wish to be reborn again and again for seven lives into this same existence in order to destroy the enemies of the court!"
[2] This statement would later be encapsulated in the four-character slogan shichishō hōkoku (七生報國; "Would that I had seven lives to give for my country!").