The deputy prime Minister of Japan (副総理, Fuku-sōri) is the second highest-ranking officer of the executive branch of the government of Japan after the prime minister of Japan, and ranks first in the line of succession to the prime minister. The office of the deputy prime minister is not a permanent position, and exists only at the discretion of the prime minister. The deputy prime minister is appointed by the prime minister and must be a member of the cabinet, for instance Taro Aso served as Minister of Finance concurrently. Should the prime minister be incapacitated or resign, the deputy prime minister does not automatically succeed to the position, but instead exercises the duties of the prime minister until the National Diet elects a successor. Tarō Asō was the longest-serving deputy prime minister. This position has been vacant since 4 October 2021. Source: Wikipedia (en)