He was assigned to defend the Azuchi Castle and fought against Hori Hidemasa as a rear guard for Mitsuhide during the Battle of Yamazaki.

He became a legend for his rapid crossing of Lake Biwa to get from Otsu to Sakamoto Castle on the back of his famous horse "Okage", after the loss and defeat of Mitsuhide's forces at Battle of Yamazaki.

He then performed his famous and unpredicted act of committing hara-kiri while writing a poem on a door with blood from his abdomen used as ink for his brush.

While much of the Akechi clan was destroyed at Sakamoto Castle, Hidemitsu's sons Miyake Shigetoshi and Tōyama Tarōgorō survived.

Shigetoshi served Terasawa Katataka at the Shimabara Uprising and was killed by the rebel forces under Amakusa Shirō, while Tarōgorō is remembered as the ancestor of the famous nineteenth-century political activist Sakamoto Ryōma.