Because Saigo was busy with national affairs and was not at home mostly, his family needed a man who could manage the master's works, therefore Kawaguchi worked as butler to deal with the outside such as attending visitors and using his calligraphy for writing letters, and worked as rusui-yaku (person representing the master during his absence) as well as teaching calligraphy and Chinese literature to Saigo's children.
西郷は国事に奔走して家を空けることが多く男手が乏しい西郷家にあって、来客の応対や能書を生かした信書連絡などもっぱら外回りの役目を果たす家令あるいは留守居役を果たすとともに、西郷の子弟の書や漢学の師ともなった。