日本新党
He was elected to the House of Representatives as a member of the Japan New Party of Morihiro Hosokawa in 1993. In 1994, he left the party and formed the "Democratic Wave" with several other young parliamentarians, but later that year joined the Sakigake Party, which was briefly part of the majority government. In 1998, he joined the Democratic Party of Japan (DPJ) when it was formed that same year.