Lifespan: Daiei 3 (1523) to 1/14 of Bunroku 4 (1595)
Title: Vice Minister of Central Affairs
Lord: Date Harumune → Date Terumune → Date Masamune
Father: Koyanagawa (Owari-no-kami) Chikamune
Koyanagawa Morimune served as a bushō during the Sengoku period. He served as the head of the Mutsu-Koyanagawa clan and a retainer of the Date clan. Morimune was the son-in-law of Date Harumune. He descended from the line of Koyanagawa Chikatomo and his great grandfather from the Muromachi period carried the same name of Koyanagawa Morimune.
In 1523, Morimune was born as the son of Koyanagawa (Owari-no-kami) Chikamune.
Morimune served the Date clan from the era of Date Harumune, the fifteenth head of the Date clan, and was granted Takahata Castle in the Okitama District of Dewa Province. Known for his bravery and intellect, Morimune served meritoriously in battle against Satomi Minbu (a retainer of the Mogami) and Ōuchi Sadatsuna, the lord of Obama Castle in the Adachi District of Mutsu Province. In 1570, after a retainer of the Date named Nakano Munetoki absconded owing to suspicions of plotting a rebellion, Morimune overlooked his departure, inviting scorn from Date Terumune, his younger brother-in-law. In 1585, after the death of Terumune, Morimune cited his age as a reason to retire. Thereafter, Morimune served as a trusted advisor to Date Masamune. In his latter years, he adopted the monk’s name of 泥播斎. On 1/14 of Bunroku 4 (1595), he died in Kyōto at the age of seventy-three.