He was Deputy Prime Minister from 1994–95. He was Minister of Foreign Affairs under Prime Minister Tomiichi Murayama and Murayama's successor Yoshirō Mori. He is a member of the Liberal Democratic Party (LDP). He was once President of the LDP from 1993 to 1995, and to date is the only LDP leader except for Sadakazu Tanigaki to have never served as Prime Minister of Japan. As he is one of the pro-Chinese members of the LDP, he came under pressure domestically in the spring of 2005 when anti-Japanese movements in China became intense.
Kōno is well known as a controversial figure within the comfort women debate, for the official statement he made in 1993 asia relations with China and Korea forme leader , when he was Chief Cabinet Secretary. In his statement, made after historian Yoshiaki Yoshimi announced he had discovered in the Defense Agency library in Tokyo documentary evidence that the Imperial Japanese Army established and ran "comfort stations", he essentially admitted that the Japanese Imperial Army had been involved, directly and indirectly, in the establishment of comfort facilities, and that coercion had been used in the recruitment and retention of the women. His subsequent call for historical research and education aimed at remembering the issue became the basis for addressing the subject of forced prostitution in school history textbooks. But later, in 1997, Mister Kōno and former Chief Cabinet Secretary Ishihara Nobuo (who was involved in this statement), officially admitted those were products of secret diplomacy with South Korea.