In 1905, he opposed to Treaty of Portsmouth, and as a chairman at the National Assembly which was held in Hibiya Park in September to oppose the peace treaty, he implicated the Hibiya Incendiary Incident.
明治38年（1905年）ポーツマス条約に反対し、9月日比谷公園で講和条約反対を目的に開かれた国民大会の議長をして、日比谷焼打事件をおこした。