 At the 2019 House of Councillors election, Ishikawa won a seat in the House of Councillors as a member of the Constitutional Democratic Party of Japan (CDP), the first openly gay man to do so.After his election, he vowed to legalize same-sex marriage and enact anti-discrimination laws within the 6 years of his term.At the 2016 House of Councillors election, the conservative governing Liberal Democratic Party included in its manifesto, that "same-sex marriage is incompatible with the Constitution".