When MINAMOTO no Yoritomo rose in arms to defeat the Taira clan in Izu Province in 1180, he joined Yoritomo with his brothers Sadatsuna SASAKI, Tsunetaka SASAKI, and Moritsuna SASAKI and defeated Kanetaka YAMAKI.
治承4年（1180年）に源頼朝が伊豆国で平氏打倒の兵を挙げると、兄弟の佐々木定綱、佐々木経高、佐々木盛綱と共にそれに加わって、山木兼隆を討つ。