After the Amago clan surrendered Gassantoda-jo Castle to the Mori clan November 28, 1566 and the Amago family fell, in order to reconstruct the Amago family, Yukimori YAMANAKA and Hisatsuna TACHIHARA, the past vassals of the family worked to let Katsuhisa AMAGO who was a son of Sanehisa AMAGO and a member of Shingu-to (party) returned to secular life from Tofuku-ji Temple in Kyoto backing him up in 1568.
1566年永禄9年11月28日に月山富田城が開城し、尼子家が滅びた後、尼子家家臣である山中幸盛・立原久綱達が尼子家再興を目指すため、1568年、京都・東福寺に逃れていた新宮党の尼子誠久の子である尼子勝久を還俗させ、擁立した。