After the overhrow of the Tokugawa, he became a head councillor in the newly established Meiji govermment. However, after a debate over an overseas policy he returned to Kochi and formed the Public Party of Patriots, which submitted to the govermment a subsequently famous memorial calling for the establishment of representative government in January,1874. In April of the same year, Itagaki organized the Rishisya (Self-help Society) which pronounced ideals of freedom and popular rights. This soon coalesced into a national movement and in 1881 Itagaki helped form, and was named head of the Jiyuto (Liberal Party). Japan's first genuine political party. In the following spring on the 6th of April he was attacked by a man with a knife. Hisa clothes stained in his own blood, he cried loudly.
This phrase became instantly famous and inspired people all over Japan in their search for political freedom.
In May of 1887 he was given the aristocratic title,hakushaku, but he argued for making such honors non-inheritable. In later years he was named Home Minister twise. In 1899 he retired from political life and then he worked for social improvement movements and for the development of traditional Japanese sports like Sumo, l-ai etc.
He died at the age of 83 on July 16,1919. Among his works are Bushido and Rikkoku no Taihon ("The Phillosopical Basis of the Nation").