Two female politicians have emerged in key roles for Tokyo's preparations to host the 2020 Olympic Games, but critics have been quick to voice concern about the new partnership.

Prime Minister Shinzo Abe on Wednesday named Tamayo Marukawa as the nation's new Olympics minister, a day after Yuriko Koike took office as the first female governor of the capital.

Marukawa, 45, and Koike, 64, are expected to work hand-in-hand as Japan prepares to stage the sporting extravaganza in four years.