At first he considered a career as a diplomat or in a trading company, but was deeply affected by reading the work of doctor and psychiatrist Yushi Uchimura.
Between 2008 and 2009, he was part of a High-Level Taskforce on Innovative International Financing for Health Systems, which had been launched to help strengthen health systems in the 49 poorest countries in the world and was chaired by UK Prime Minister Gordon Brown and World Bank president Robert Zoellick.
[6] In 2016, he was appointed by United Nations Secretary-General Ban Ki-moon to the Global Health Crises Task Force, jointly chaired by Jan Eliasson, Jim Yong Kim, Margaret Chan and Helen Clark.
[6] In February 2020, Omi was appointed vice chair of a government panel of experts on COVID-19 pandemic in Japan,[7] and was a top advisor for the 2020 Summer Olympics organisation committee.
[9] He also testified at a parliamentary committee that "if they were to be held during a pandemic, it is the organizers' responsibility to scale them down as much as possible and strengthen the management system",[10] and on 19 June warned that due to a possible spike in infections in Tokyo, the games should be hosted without any kind of public.