Amagai 【天海】4 The Japanese surnames etymology dictionary.
① Tochigi-ken Oyama-shi Origin of rain gull (Amagaya). A place name with a record in the notation of "Nyugaya" during the Warring States Period. Tradition in Shimane-ken western part (formerly Iwami-kuni). Fukui-ken Fukui-shi major was in the Edo era in the Fukui clan of the clan office, Gunma-ken Takasaki-shi Takamatsucho in the clan san Takasaki of the clan office. 雨谷 reference.
② Abstract . Synthesis of Tengu and Nishitani. Wakayama-ken Wakayama-shi in 1948 changed the name "Tengu" with "Tengu" and "Tani" from the Nishitani family name of the birthplace. The pronunciation is Amatani. It is unknown whether Tengu will exist. 西谷 reference.