The Shima clan was considered to be a resident landholder around present-day Heguri-cho, Ikoma County, Nara Prefecture.

Sakon served the Hatakeyama clan who were the Shugo (Governors) of Kawachi Province.

Later in 1577, Sakon became one of the two primary samurai officers under Tsutsui Junkei alongside Matsukura Shigenobu.

He fought against Hosokawa Tadaoki and was shot by riflemen led by Kuroda Kanbei's son, Nagamasa, and forcing him to retreat.

His fourth son, Shima Kiyomasa, fighting within Otani Yoshitsugu's ranks, was killed by an 'Eastern' samurai named Takagi Heizaburō.