Yamanashi Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Yamanashi Prefecture has a population of 817,192 and has a geographic area of 4,465 km². Yamanashi Prefecture borders Saitama Prefecture to the northeast, Nagano Prefecture to the northwest, Shizuoka Prefecture to the southwest, Kanagawa Prefecture to the southeast, …Yamanashi Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Yamanashi Prefecture has a population of 817,192 and has a geographic area of 4,465 km². Yamanashi Prefecture borders Saitama Prefecture to the northeast, Nagano Prefecture to the northwest, Shizuoka Prefecture to the southwest, Kanagawa Prefecture to the southeast, and Tokyo to the east.