Kuroko are clad totally in black and function as stage hands in traditional Japanese plays. They also operate puppets in bunraku and awaji theater. Because they are clad totally in black and their faces are masked by a black cloth they are difficult to see on stage, which is intentional. The audience is supposed to treat them as if they are invisible.

Relevance to Ranma ½

When Ranma and Akane are performing Romeo & Juliet Soun comes onstage wearing a solid black costume to help Ranma with his lines. Soun is playing a Kuroko, which is someone who takes care of the props and actors onstage. Kuroko's play a large part in the life of Ryoko Mendo from Rumiko Takahashi's other classic series Urusei Yatsura.