Rank in Judo are ranked in ascending numerical order. The ninth ("kudan") and tenth degree black belt ("jūdan") and, theoretically, those higher, have no formal requirements. Only 15 individuals have been promoted to the rank of Kōdōkan 10th dan. On January 6, 2006, three individuals were promoted to this rank simultaneously: Daigo Toshirō, Ichirō Abe, and Ōsawa Yoshimi. This is the most ever at the same time, and the first in 22 years. No one has ever been promoted to a rank higher than 10th "dan", but in theory the Judo rank system is not limited to 10 degrees of black belt. The
Kosen judo ordinary contenders, a captain and a vice-captain, and five replacements in case of injuries or retirements. Every match is composed of a single, six-minute round, changed to an eight minute round when the contenders are captains or vice-captains. The league is hosted as a "kachi-nuki shiai", meaning every winner stays on the mat to face the next member of the rival team. At the end of the event, victory is given to the team with the highest numbers of matches won or with the last man on the field. Kosen judo Today, the term "kosen judo" is frequently used to