As the kanreidai (representative of a shogunal deputy) and protector of the shogun, and the Shugo of the seven provinces of Suo, Nagato, Iwami, Aki, Chikuzen, Buzen, and Yamashiro, he was one of the great men of the early the Sengoku Period (Period of Warring States) prior to the appearance of Nobunaga ODA.
室町幕府の管領代となって将軍の後見人となり、周防・長門・石見・安芸・筑前・豊前・山城の7ヶ国の守護職を兼ね、織田信長らが登場する前の戦国時代前期の事実上の天下人として君臨した。