As a youth, Jigero Kano first learned the basics of Jujutsu from Teinosuke Yagi. Later, he studied tenshin shinyo ryu Jujutsu under Hachinosuke Fukuda and Masatomo Iso, as well as kito ryu Jujutsu under Tsunetoshi Iikubo so he was familiar with the secrets of both schools.
After founding Judo, Kano researched other styles of Jujutsu, including examining their densho. From his findings, Kano revised the Judo ranking system, creating ten ranks with relatively short intervals between them to keep students interested in progressing through them. In 1883, Kano further divided students into two groups, the non-graded "mudansha" (kyu ranks) and the graded "yudansha" (dan ranks). Grade certificates were issued starting in 1894.
Black belts were not worn as symbols of Judo dan grade until about 1886. However, these belts were not the same as belts worn today. Since Kano had not yet invented the Judo uniform, Judo students practiced in a "kimono" (the traditional Japanese robe) and wore the wide belt that is still worn with the formal kimono. In 1907, Kano introduced the modern Judo uniform and belt, but he still only used white and black belts.