Yamagata Masakage also known as Obu Masakage was a Japanese samurai warrior of the Sengoku period. He is known as one of the "Twenty-Four Generals of Takeda Shingen". He was famous for his red armour and skill in battle, and was a personal friend of Takeda Shingen. He was the younger brother of Obu Toramasa, who was also a retainer of Shingen, leading the famous "red fire unit".