The hairstyle worn by the courtesan was reserved for the highest ranking in their profession. It is referred to as datehyōgo (伊達兵庫). It appears in Utamaro prints mainly in the last decade of the 18th century. Above is a link to an Utamaro print in the Museum of Fine Arts, Boston showing an oiran with a similar, but related, hairstyle.
We have also added a link to a Chōki print from ca. 1795, also in Boston, showing a courtesan wearing a variation on this style. Cecilia Segawa Seigle in her book on the Yoshiwara noted that the most precious thing in a prostitutes possession was her hair, followed by her robes.