The Judan Championship is sponsored by large daily national newspaper, the Sankei Shinbun (originally known as the Sangyo Keizai Shinbun). It is the successor to the Hayago Meijin.
Top prize is 10.6 million yen. Runner-up gets one fifth as much. Game fees are graduated not just according to the stage of the event but also according to rank.
The structure of the tournament is unusual in that it incorporates a repechage, though it has been copied several times. The purpose is to ensure that the strongest players do not suffer from an accidental loss.
The main section begins with a 16-player knockout (the Winners' Section), but the losers cross over to a parallel Losers' Section knockout. The level at which they enter depends on the level at which they were knocked out of the Winners' Section.
The winners of the two sections eventually play off to decide who challenges the title holder in a best-of-five (in Term 1, however, the play-off was a best-of-five to decide the first holder). With one exception, a player thus drops out only once he has lost two games.
The exception is the winner of the Winners' Section. If he loses the play-off against the winner of the Losers' Section, he gets no second chance.
All those who win two or more games in the main section retain their places the following year. The other eight players drop back to the qualifying stage.
The event is open to all pros from the Nihon Ki-in and the Kansai Ki-in. The preliminary stages are divided into three. First is a knockout tournament for all 1-dans to 4-dans (giving four from the Nihon Ki-in and two from the Kansai Ki-in), and then comes another knockout for the Stage 1 qualifiers and all 5-dans to 9-dans, to find 24 qualifiers for the third stage knockout, where they are joined by the eight players demoted from the main event.
In Term 1, all 9-dans (11) seeded to the main event.
Time limits are now 5 hours each but used to be 6 hours each. Komi is 5.5 points.
Judan means 10-dan (normally 9-dan is the highest rank awarded).
The Hayago Meijin (1956-1961), also sponsored by the Sankei Shinbun (then briefly known as the Sankei Jiji; the name was changed to Sankei Shinbun in 1956), was originally comprised of separate tournaments for East and West Japan, and the respective winners (meijins) were pitted against each other in a telegraph match for the overall title. This was because the Sankei Jiji had separate editions in Tokyo and Osaka.
Although Hayago means "quick go" or "lightning go", in those days it meant games of 5 hours each played in one day, rather than the 10 hours and two days of the main title matches. The final was a best-of-three and komi was 4.5 points.