Since January 2022, Mr. Yamasaki has been involved in the planning of social security policy in general. This includes countermeasures against Japan’s declining birthrate, as Special Advisor to the Cabinet and Director-General of the Headquarters for Building Social Security for All Generations. He also serves as director of the Institute for Population Strategy at the International University of Health and Welfare in Tokyo.

He started his career at the Ministry of Health, Labor and Welfare（MHLW) after graduation from the Faculty of Law, University of Tokyo. He has served as Deputy Director of the Headquarters for the Care of the Elderly at MHLW, Director-General of the Cabinet Office, Executive Secretary to the Prime Minister, Director-General of the Social and Aid Bureau at MHLW, and Commissioner of the Headquarters for Overcoming Population Decline and Vitalizing the Local Economy.

During his government career, Mr. Yamasaki was involved in the planning, implementation and review of the Long-term Care Insurance system, which came into effect in 2000. He was also in charge of youth employment measures, support for the needy, countermeasures against the declining birthrate, and planning measures for revitalizing Japan at the regional level.

In July 2018 Mr. Yamasaki was appointed Ambassador Extraordinary and Plenipotentiary to Lithuania. In September 2021 the Lithuanian government awarded him with its Diplomatic Star Medal for his achievements there.

Mr. Yamasaki is also an author of several books about Japanese society. His most recent book is The Population Strategy Bill - Is there a way to stop population decline? , Nikkei Publishing.Inc.,2021.