Kai Kokushi (甲斐国志, Official Records of Kai Province) is a compilation of information regarding Kai Province (present-day Yamanashi Prefecture) It covers much about the region, culture, and history of Kai Province, including feudal lord Takeda Shingen and those who served under him. Written in 124 volume. It was compiled in its entirety in 1814 through the cooperation of a few individuals including Matsudaira Sadamasa (松平定能), who was the main compiler of information.
The following covers the written record on Hara Hayato Sa Masatane (原隼人佐昌胤), and the passing down of the title “Hayato”. This is taken from the 5th section of Jinbutsu Bu (人物部, Notable Individuals) from the 96th volume. Originally this information was used as research material for both a translation project and an article written almost 4 years ago.