Sadahisa served the Ogigayatsu-Uesugi clan and built Takiyama castle. After the Uesugi defeat at Kawagoe in 1545, Oishi was made to accept the authority of the Hôjô. He was murdered and was succeeded by Hôjô Ujimasa's 2nd son Ujiteru. After the fall of the Hôjô, his sons Yoshinaka and Sadakatsu came to serve Ôkubo Nagayasu.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005