Shinohara Nagashige served as a bushō during the Sengoku period. He was a retainer of the Miyoshi clan. Nagashige served as the lord of Akizuki Castle in the Awa District of Awa Province.
In 1555, Nagashige was born as the son of Shinohara Nagafusa, a powerful bushō based in Awa. The Shinohara clan served as hereditary retainers of the Miyoshi clan, the military governors of Awa. In the era of Nagashige’s father, Nagafusa, the Shinohara supported the youthful head of the Miyoshi clan, Miyoshi Nagaharu and his younger brother, Sogō Masayasu in neighboring Sanuki Province. Nagafusa led forces from Awa and Sanuki on numerous deployments to the Kinai. Nagashige participated with his father in many battles and was praised for his achievements.
In the tenth month of 1570, Nagashige landed in Settsu Province for the Battle of Noda and Fukushima Castles. Together with his uncle, Shinohara Jiton, he signed a written ban against the Honkō Temple in Amagasaki in Bizen Province. In the first month of 1571, he returned to Shikoku to issue a ban against the Saikō Temple in Sanuki, and, in the twelfth month of 1572, a ban against the Rikyū-Hachiman Shrine in Ōyamazaki in Yamashiro Province.
Later, there was a falling out among Nagafusa, Jiton (Nagafusa’s younger brother), and Nagaharu (the eldest son and heir of Miyoshi Jikkyū). In the fifth month of 1573, the combined forces of Nagaharu and Sogō Masayasu laid siege to the base of Nagafusa at Uezakura Castle in an event known as the Siege of Uezakura Castle. After a siege of the castle lasting approximately two months, early in the morning on 7/16, Nagafusa and Nagashige launched a surprise attack against Masayasu’s encampment, but were defeated and Nagashige was killed by a retainer of the Kōzai clan of Sanuki named Uematsu Sukehisa. He was nineteen years old.