The 2020 Olympic and Paralympic Games are expected to be the most important project during Koike's four-year reign.

Koike, President of the Japanese Weightlifting Federation and a former Defence Minister in the Japanese Government, was chosen as the city's first female Governor in the election yesterday.

Travelling to Brazil for the handover of the Flag from Rio Mayor Eduardo Paes will be her first international assignment.

"It's the Governor's duty," Koike said. 

"I think I will just have to make a rush trip."

Running against 20 other candidates, the 64-year-old Koike eclipsed her nearest rival by more than a million votes.

The election took place after former Governor Yōichi Masuzoe stepped down last month following allegations he had embezzled public funds for personal expenses.

The turnout for the election was low at about 27 percent but voters overwhelmingly backed Koike, a one-time television news anchor who speaks English as well as Arabic, which she learned as a student in Egypt.

Koike, though, could face expulsion from the Liberal Democratic Party (LDP) after she ran as an independent following the party's decision to back another candidate, Hiroya Masuda.

Hakubun Shimomura, special adviser to LDP President and Japanese Prime Minister Shinzō Abe, claimed Koike's campaign had been an "anti-party act" and they would discuss how to punish her.

The LDP is the ruling party in the Tokyo Metropolitan Assembly.

Koike promised she would work with them in the build-up to Tokyo 2020.

"We have both been selected by the people of Tokyo," she said.

"I want to look for a connection with them and ask for their cooperation."