- Japanese: 一色 義定 (Isshiki Yoshisada)
Yoshisada took over as head of the Isshiki clan when his father Yoshimichi was forced to commit suicide in 1579 by Hosokawa Fujitaka. He continued to resist until he accepted a truce with Fujitaka and married one of the latter's daughters. Yoshisada was overthrown and killed in 1582 by his uncle Isshiki Yoshikiyo, who was in turn destroyed by the Hosokawa.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005