After joining the Ministry he was sent to Oxford University for two years to receive training in the English language and international politics.

[1][2] Tomita's diplomatic career includes postings at the OECD Delegation in Paris and at the Japanese embassies in South Korea and the United Kingdom.

In November 2015 he was appointed Ambassador to Israel and served until June 2018, after which he acted as Japan's sherpa for the 2018 G20 summit.

In an interview, he stated his familiarity with Obama-era officials led to his appointment as ambassador after the election of Joe Biden.

[7][8] Tomita has published two books in Japanese on British prime ministers Winston Churchill and Margaret Thatcher, the latter of which received the Shichihei Yamamoto Award in 2019.