Etymology and distribution of 口開.

Koukai 【口開】^{レベル2
About 10}  The Japanese surnames etymology dictionary.

Nagasaki-ken , Fukuoka-ken Fukuoka-shi . There is sagas on the name of a man. It was in the Edo period in Nagasaki-ken Hirado-shi . Tell the story that Mr. Goto's descendant was called. 五島 Gotou reference.