This paper examines the process how English study replaced Dutch study,which was the main source for getting Western knowledge, cultures and technologyduring the Tokugawa period. In doing so, the paper focuses on Sen Tsuda（1837-1908）, who was one of intellectuals living in the same period as YukichiFukuzawa （1835-1901）. Sen Tsuda is known as the father of Umeko Tsuda （apioneer of womenʼs education）, but he is less-noted in general Japanese history.Yet, he was a well-known agriculturist at the time and made great efforts for themodernization of Japan, just like Fukuzawa. In opening up Senʼs life, the acquisitionof English language played an important part. It is quite intriguing for usEnglish teachers to look at Senʼs touching efforts to learn English at the timewhen it was difficult to get helpful dictionaries. The paper sheds light on his painfulefforts by citing his own writings in the journals published at the time. Wewill also examine how the mastery of English contributed to his achievements inhis later life.