He was an academic assistant at the University of Tokyo from 1971, and later spent several years in Europe as a research fellow at the University of Paris (1973-75) and University of Geneva (1976-78).
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He met with Chinese state councilor Dai Bingguo in March 2011 following the resignation of Foreign Minister Seiji Maehara to reassure the Chinese government about Japan's stability.
Following the resignation of Tokyo governor Naoki Inose on December 19, 2013, she was widely rumored to be a potential candidate for the gubernatorial election expected to be held in February 2014, along with Yuriko Koike, Hakubun Shimomura, Hideo Higashikokubaru and Yoichi Masuzoe.