Shimazu clan
, the son of Iriki-In Shigetoshi, was a vassal under the Shimazu clan of Satsuma. The lord of the Shimazu clan, Shimazu Katsuhisa, suffered the rebellion of a kinsman, Sanehisa, and was forced to flee Satsuma during 1526. The Shimazu clan head was then passed on to Katsuhisa's eldest son, Shimazu Takahisa. Even though Takahisa was the new head, Katsuhisa still had authority over a good amount of land. Considering Shigetomo's lands were very close to that of the Shimazu's, he found himself in conflicts between the Sanehisa around Momotosugi.