Naosuke II was a man who had arbitrarily signed the Five Nations Treaty of Ansei without imperial sanction from the Emperor Komei, and settled a problem of heir of Shogun caused between the Hitotsubashi group (group supporting Yoshinobu from the Hitotsubashi-Tokugawa family) and the Nanki group (group supporting Yoshitomi from the Kisyu-Tokugawa family), and who had also suppressed the opposition to the Ansei no Taigoku (the suppression of extremists by the Shogunate); his opposition was a group of radical roshi (masterless samurai) from the Mito clan, including Taichiro TAKAHASHI and Magojiro KANEKO, who were strongly opposed to the confinement and punishment of Nariaki TOKUGAWA, the father of the lord of domain and thus left the clan.
孝明天皇から勅許が得られないまま独断で安政五カ国条約に調印し、一橋派・南紀派の将軍継嗣問題を裁決したうえ、安政の大獄で反対勢力を弾圧していた井伊直弼に対し、藩主の父・徳川斉昭への謹慎処分などで特に反発の大きかった水戸藩では、高橋多一郎や金子孫二郎などの過激浪士が脱藩した。