On 31 May 2017, in advance of the upcoming local elections, Koike resigned from the Liberal Democratic Party and officially became the leader of Tomin First no Kai (Tokyoites First). Koike founded the group in 2016 in preparation for the elections and formed an alliance with Komeito in an effort to secure a governing majority in Tokyo's parliament. On July 3, 2017, the alliance took a majority in the prefectural election, pushing out the Liberal Democratic Party with a combined 79 seats of the 127-seat assembly.