Yumi Hiwatari was a Visiting Fellow at CIS in 2005–06. She is a Professor of International Relations at Sophia University in Tokyo and has written widely on U.S.-Japan relations and Japanese defense politics. Her previous research interests concern the comprehensive review of Japan’s defense policy, especially the policy changes that took place during the Koizumi administration and their impact on Japan’s Self-Defense Forces. She has an essay on that topic in Breakthroughs, Spring 2006. In 2012, Hiwatari finally finished her book on Japan's national security, Defending Strategy: Rethinking Japan's National Security (Senshu Bouei Kokufuku no Senryaku). The publisher is Minerva Shobo Japan. The book consists of five chapters, including strategy, U.S.-Japan alliance, defense budget, structural reform, and civil-military relations. It is available only in Japanese.
Her current research topic is Koizumi's structural reform and national security policy making: implication of domestic political reform for Japan's national security policy.
She received her Ph. D. at the University of Tokyo in 1989. She was a Visiting scholar at UCLA from 1991-1993.