IGUCHI met a missionary, named Elmer who was an English teacher while he was in Prefectural Jinjo Chugakko (Ordinary Middle School) Matsumoto Branch School (currently, Matsumoto Fukashi High School), and was already influenced by Christianity.
井口は県尋常中学松本支校（現・松本深志高等学校）時代、英語教師のエルマー宣教師に出会い、すでにキリスト教の感化を受けていた。