Her father, Yūjirō Koike, was a foreign trade merchant who handled oil products. He was also involved in politics, supporting Shintarō Ishihara and the Tatenokai in 1960s, and ran for a national election to no avail in 1969."Oyaji no Senaka", Asahi Shimbun Morning Edition, August 24, 2008 He occasionally told Yuriko his opinion that it was essential for Japan to strengthen relations with Arab countries in order to ensure a stable petroleum supply lest the resource-poor Japan be thrust into war for oil again. His word encouraged her to decide to study in Egypt to master Arabic."Kikase te Anata no Mottainai", Shūkan Josei, Shufu-to-Seikatsusha, September 12, 2006