In 1224, when Masamura was 20 years old, his father Yoshitoki died suddenly; then Masamura's mother Iga no kata plotted to make him regent, and the Incident of the Iga clan occurred.
1224年、20歳の時に父義時が急逝すると、母伊賀の方が政村を執権にする陰謀を企てたという伊賀氏の変が起こる。