Tokutaro Nakai joined the Ministry of Finance Japan in 1985 serving as the Chief of the Budget Bureau. then from 1999 to 2002, took a secondment to the Toyama Prefectural Government, contributing to the advancement of Japan Sea Studies while holding positions such as Director of the Department of Living Environment. In 2002, Tokutaro played the role of Chief of the Public Relations Office at the Ministry of Finance Japan, and in 2004, embarked on a new path as a professor at the Institute of Medical Science, The University of Tokyo. In 2009, he was appointed to Planning Officer at the Ministry of Finance's Financial Bureau, followed by the position of Director of the Budget Bureau in 2010. After being transferred to the Ministry of the Environment in July 2011, held various roles including General Affairs Division Manager at the Environmental Policy Bureau, Deputy Director-General of the Minister's Secretariat (Environmental Policy Bureau), and Director General for Environmental Policy, to name a few. After serving a diverse career, he assumed the role of Deputy Minister of Environment, retiring in July 2022. Post-retirement, Tokutaro is taking on advisory roles for private companies with a desire to actively contribute to decarbonization.