Head of the Mimura clan of Bitchu-Matsuyama. In 1533 he moved his base to Kakushu Castle (also called Nariwa Castle), extending his power across eastern Bitchu. In 1561 he seized Bitchu-Matsuyama Castle and moved his base there, leaving Kakushu Castle to his retainer Mimura Chikashige. Just as he neared unifying Bitchu, he was assassinated in 1566 by an agent of Ukita Naoie of Bizen, shot with a matchlock gun — one of Japan's rare recorded firearm assassinations.

A pragmatic warlord who governed eastern Bitchu from Kakushu Castle for 28 years, meeting a dramatic end when he was assassinated amid his rivalry with Ukita Naoie.

Using Kakushu Castle as his base, he carved out eastern Bitchu and made the Mimura clan the region's dominant power. After his assassination, his son Motochika wavered between the Mori and Oda, and the Mimura clan perished in the Bitchu Rebellion of 1575.