Oza (王座) literally means "throne". It is one of the seven top professional titles in Japan.
The tournament is sponsored by Nihon Keizai Shinbun, and carries a first prize of 10.4 million Yen. All players in the Nihon Ki-in and Kansai Ki-in can participate.
In the current format, the title holder is challenged by the winner of a preliminary tournament. The final is played to a best of five, usually in November and December.
Check out the OzaWinnersList.
--Stefan