He decided to study Rangaku when his elder brother encouraged him to learn the Dutch language on the grounds that the government had been demanding gunnery techniques after the arrival of "black ships", but Dutch gunnery should be studied through books written in Dutch.
黒船来航により砲術の需要が高まり、オランダ流砲術を学ぶ際にはオランダ語の原典を読まなければならないがそれを読んでみる気はないかと兄から誘われたのがきっかけであった。