Yuriko Koike received more than 2.9 million votes in Sunday's election for Tokyo governor, beating former bureaucrat and fellow member of Prime Minister Shinzo Abe's party Hiroya Masuda, as well as liberal journalist Shuntaro Torigoe.
Koike were running as independent candidate, without getting an approval from Abe's Liberal Democratic Party before announcing her candidacy for city governor.
The first challenge on her way would be Tokyo's preparations to host the 2020 Olympic Games. Construction of the main stadium has been delayed and the original logo for the games had to be scrapped after plagiarism accusations. After the resignations of the city's two previous governors, Koike will be responsible for saving Tokyo's reputation as host for the games.
"I will lead Tokyo politics in an unprecedented manner, a Tokyo you have never seen," Ms Koike told her supporters.
"I would like to move forward with a metropolitan administration such as has never happened, never been seen, together with all of you," she added.
As her first duty she will travel to Rio de Janeiro when the Olympics begin to accept the Olympic flag as the next host. "The Olympics are right in front of us. I want to use them as a chance to build a new Tokyo for beyond 2020," Koike said.