According to their family tradition, the first head of the Inui family Masanobu INUI was "a grandson of Nobukata ITAGAKI, a commanding officer who served Shingen TAKEDA of Kai Province.
家伝によると乾氏の初代・乾正信は、「甲斐の武田信玄に仕えた部将・板垣信方の孫である。