Then, Gengo studied advanced mathematics in Dutch with two of his mentors Yadabori and Arai Ikunosuke , and published a book about naval tactics. He also learned both English and French. In 1859, he became a vassal of the Shogunate and was appointed as a warship training assistant. The following year, Gengo also served as a guardsman in Yokohama. In 1861, Gengo became professor of naval training.