Most of those who joined the Thursday protest were connected to Shinto shrines, Kyodo News reported.
The government has drafted a bill that would allow a woman to ascend to the throne, and permit her descendants to follow her. The matter is of great interest in Japan, as no male heir has been born into the royal family since 1965.
However, the Shinto Association of Spiritual Leadership, in a petition addressed to Prime Minister Junichiro Koizumi, said, "There is no urgent necessity to revise the basic principle of the imperial succession right now."
Yoshinori Miyazaki, head of the association, said Japan's parliament should not rush in making such a revision. But in his speech to parliament Friday, Koizumi said the government would go ahead with its plan to submit the bill.