Hara Masatoshi served as a bushō during the Sengoku period. Masatoshi was a retainer of the Kai-Takeda clan and hereditary chief retainer. He was the founder of the Hara Hayato-no-suke family. Other names included Kunifusa, Tanemoto, and Kaga-no-kami. His son was Hara Masatane.
Masatoshi’s achievements cannot be entirely confirmed from historical accounts. Masatoshi served as a chief elder of the Kai-Takeda clan from a line of hereditary retainers originating from the Hara who were a branch of the Toki clan of Mino Province. The family of Hara Toratane and Yokota Yasukage, who served as commanders of the ashigaru, or foot soldiers, originated from a branch of the Chiba clan of Shimōsa Province and the relationship between them and the Hara clan of Masayoshi is unclear.
Masatoshi controlled the Takahata township in Kai, serving two generations of the Takeda – Takeda Nobutora and Takeda Harunobu (Shingen). In battles, he decided the battle formations and the location for setting-up camps. He further served as the director of the cavalry, reporting on the battle situation. Masatoshi was highly regarded by Nobutora and Harunobu. After being ousted by Harunobu, Nobutora informed Imagawa Yoshimoto that the skilled archers in the Takeda family included Hara Masatoshi, along with Itagaki Nobukata, Amari Torayasu, Obu Toramasa, Oyamada Toramitsu, and Morozumi Toramitsu. Commanders of the ashigaru included Yokota Takatoshi, Hara Toratane, Tada Sanpachirō, and Obata Toramori.
Masatoshi died in 1549 and the headship of the clan was inherited by Masatane (Hayato-no-suke), who also assumed the role as director of the cavalry.