From this, he became aware of the concept of Sonno Joi (slogan advocating reverence for the Emperor and the expulsion of foreigners) and formed a plan to take over Takasaki-jo Castle and fire Yokohama to topple the Bakufu (Japanese feudal government headed by a shogun).
その影響から文久3年（1863年）に尊皇攘夷の思想に目覚め、高崎城を乗っ取り、横浜を焼き討ちにして、幕府を倒す計画をたてる。