Sukemasa was the lord of Iwatsuki castle in Musashi and a vassal of the Uesugi. He came to accept the authority of the Hôjô but later rebelled and came to rely on the Satomi, with whom he was defeated at Konodai in 1564. He then took up with Satake Yoshishige.
References
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005