Etymology and distribution of 兠坂.

Tosaka 【兠坂】^{レベル1
Very rare}  The Japanese surnames etymology dictionary.

Kagoshima-ken Ooshima-gun Tokunoshima-chou · Hyougo-ken Koube-shi . Terrain . "Oka" was added to Saito which is the surname of Amagi archipelago of Kagoshima-ken . Estimated at the time of returning to Japan in 1953. 治 Haru reference.