He resigned from the
Ministry of Finance in 1950, and ran as a
Liberal Party candidate in the
second regular election for the
House of Councillors held that same year, winning his first election. His experience and policy-making skills were highly evaluated by
Hayato Ikeda, who was the
Minister of Finance at the time. Following Ikeda's resignation due to illness in November 1964, Aichi continued to serve as Minister of Education and Director-General of the Science and Technology Agency in the
First Satō Cabinet, and was again appointed as the
Chief Cabinet Secretary after a
cabinet reshuffle. He was later appointed
Minister for Foreign Affairs in the
Second Satō Cabinet after a reshuffle in 1968, and he retained this position in the
Third Satō Cabinet. As Minister for Foreign Affairs, he visited the
United States in September 1970 to attend the
United Nations General Assembly in
New York City. Using this as a foothold, he was in charge of negotiations between Japan and the United States for the return of
Okinawa, which led to the signing of the
Okinawa Reversion Agreement in 1971. When Satō retired after a long administration, he supported
Kakuei Tanaka instead of
Takeo Fukuda, whom Satō had considered as his successor. Aichi then drafted policies for Tanaka's candidacy for the LDP presidential election. In July 1972, Tanaka was elected
President of the LDP and became
Prime Minister. On 22 December 1972, the
Second Tanaka Cabinet was formed, and Aichi was appointed
Minister of Finance. Tanaka appointed Aichi, a proponent of proactive fiscal policy, during this most difficult period as the "trump card" of his administration, as he highly valued Aichi's abilities. In February 1973, as the
Smithsonian system was completely collapsing, Aichi decided to move the
yen to a
floating exchange rate system which led to a major shift in foreign exchange transactions. Furthermore, the
1973 oil crisis, which was caused by the
Yom Kippur War, had caused extreme shortages and inflation due to an overheated economy. In the midst of all this, Aichi actively visited various countries and promoted
economic diplomacy. ==Death==