Yukio Hatoyama was a former Prime Minister of Japan, holding office from 2009-2010. He also served as President of the Democratic Party of Japan (DPJ, 民主党) from 1999-2002 and 2009-2012, and he was a member of the House of Representatives from 1986-2012. In the 2009 general election of the House of Representatives, the Hatoyama-led DPJ won a majority of seats, taking power from the LDP. He did not run in the 2012 House of Representatives general election and retired from Diet membership.

Hatoyama published a partial constitutional draft in 2005. He emphasized the importance of Japan's cooperation with Asian countries and potential economic unification among the countries, and he proposed specifying the right of self-defense in the revised constitution and expanding the scope of the Self Defense Forces' involvement in international cooperation. He also stated that Japan should adopt a unicameral system, and that executive power should be returned to the prime minister.