[2] Tanaka was a professor of international politics at The University of Tokyo's Institute for Advanced Studies on Asia from 1990 to 2012 and from 2015 to 2017, and served a previous term as president of JICA from 2012 to 2015.

Tanaka's academic research has been interdisciplinary, comprising theoretical essays, historical description, and computer programs designed to analyze and predict developments in international politics.

[3] Having returned to Japan in 1981, Tanaka joined the Research Institute for Peace and Security (RIPS), where he was mainly in charge of editing an annual report, “Asian Security.” Influenced by the work of Professors Inoki Masamichi and Kosaka Masataka, then two of Japan's most prominent scholars of international politics, Tanaka—who had been mostly occupied with theoretical work and computer programming until then—came to acknowledge that analysis of current affairs was an “important area of work for scholars of international politics.” In the summer of 1982, as the Textbook Problem came to strain the relations between Japan and China, Tanaka wrote a paper examining the reasons behind China's vocal objection to Japanese textbooks.

In 1994, Tanaka received the Ushiba Fellowship and spent a year at St. Antony College, Oxford, where he dedicated most of his time to the manuscript of a book speculating on the direction of the contemporary world system, Atarashii chūsei: 21-seiki no sekai shisutemu (Tokyo: Nikkei Keizai Shimbun Shuppansha, 1996), and translated as The New Middle Ages: The World System in the 21st Century (Tokyo: The International House of Japan, 2002).

His works and activities encompass wide-ranging fields, including diplomacy, security, politics and economics, and he has been involved in making various proposals to the government.

"[6] Among the many projects the agency oversaw, Tanaka was involved in the comprehensive peace agreement signed in March 2014 between the Philippine government and the Moro Islamic Liberation Front (MILF).

The agreement ended two decades of negotiation, and JICA soon began implementing several “quick impact” projects in the area to improve the prospects of a lasting peace in the region.