He formed the Constitutional Political Party with Taisuke ITAGAKI and others in June 1898, received an official appointment as the first Prime Minister from an out-of-domain faction, then formed the first political party Cabinet in Japan.
明治31年（1898年）6月に板垣退助らと憲政党を結成し、同年6月30日に藩閥以外からでは初の内閣総理大臣を拝命、日本初の政党内閣を組閣した。