He joined the Japan New Party (JNP) shortly after it was established while attending university and participated in the election campaign.

He resigned and served as secretary to Shinji Tarutoko, who was a member of the House of Representatives.

Also, he served as secretary to Tsutomu Okubo, who was a member of the House of Councilors.

In the 2009 Japanese general election, he was the Democratic Party candidate for the Fukuoka 8th district.

Since two former members of the Liberal Democratic Party (LDP) ran for office as independents, Gōsei was likely to win the conservative split.