Iwao mentored Tsao, setting aside his duties at Imperial University in Tokyo for a little while every week to visit the Toyo Bunko. There he tutored Tsao in person, guiding him in the use of unpublished Dutch documents in his research. Iwao would continue the lessons until he left for home in the evening, earning Tsao's undying gratitude for his solicitous care.
岩生成一還收他為「關門弟子」，每週撥冗從自己服務的帝國大學到東洋文庫，把會議室關起來，為他個人講授課程、指導他利用荷蘭未刊文書進行研究，到了傍晚岩生教授要返家前，仍然諄諄教誨，慇勤照顧，令曹永和一生感念。