開口一番 かいこういちばん Meanings Adverb at the very beginning of one's speech; immediately upon opening one's mouth (to speak); before anything else; first of all Kanji 開 open. Read as カイ. 口 mouth. Read as コウ. 一 one. Read as イチ. 番 number. Read as バン. Word lists Yojijukugo (四字熟語) Jinuma: Japanese Dictionary · Word lists