Lifespan: Tenbun 13 (1544) to 9/20 of Eiroku 8 (1565)
Clan: Shinagawa (an illegitimate branch of the Ki family)
Lord: Masuda Fujikane
Father: Shinagawa Kazunaga
Children: Katsusada, daughter (wife of Akagari Jochiku)
Shinagawa Masakazu served as a bushō during the Sengoku period. He was a retainer of Masuda Fujikane, a kokujin, or provincial landowner, in Iwami Province. Masakazu is also known under the names of Shinagawa Daizen, Taragi Ōkaminosuke, or Shinagawa Shishinosuke.
In 1544, Masakazu was born as the son of Shinagawa Kazunaga. Through a relative by the same name of Shinagawa Masakazu, his father, Kazunaga, served the Masuda clan of Iwami. It is surmised that Masakazu (of this profile) received his name from this relative.
Masakazu was known in Iwami as an expert archer and of great physical strength, so he became a mainstay in battles serving under the command of Masuda Fujikane. Seeking to oppose Yamanaka Yukimori, a renowned commander in the Amago army, Masakazu adopted the name of Taragi Ōkaminosuke. In 1565, he participated in the Second Siege of Gassantoda Castle. In the course of this battle, Masakazu engaged Yukimori in a one-on-one duel on a sandbar in the Hirose River in Izumo but lost the fight and was killed.
There are various accounts regarding the details of the duel. According to records from the Mōri, Masakazu initially had the upper hand but Akiage Munenobu interfered and then he was killed by Yukimori. According to records from the Amago, Masakazu attempted to shoot an arrow at Yukimori, but Munenobu criticized him and shot an arrow that broke Masakazu’s bow, so after engaging in a straightforward duel, he was killed by Yukimori. This event is known as the One-on-One Duel between Yamanaka Yukimori and Shinagawa Masakazu.
His grave is in the City of Yasugi in Shimane Prefecture, but was abandoned. In 1917, his descendant named Shinagawa Yūtarō had a stone monument made with a title from Yamagata Aritomo (a military commander and politician from the Meiji and Taishō periods) and epitaph from Hirata Tōsuke (a political leader from the Meiji and Taishō periods).