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
Dan (rank) always use the term Duanwei. Korean martial arts lacked a grading system up until the Japanese occupation (1910–1945) during which a variety of Japanese martial arts were introduced into the Korean school system, most notably judo, karate-do and kendo. After the occupation ended, newly emerging martial arts like taekwondo, tang soo do, soo bahk do and hapkido adopted the dan (단, 段) and "geup" (급, 級) ranks. The dan rank system is also used by "baduk" players. Nowadays, the Korea Taekkyon Association also issues dan ranks to "taekkyeon" practitioners. Someone who has received a dan rank is called a "yudanja"