Usobuki, also known as Hyotoko, is the male character of traditional Japanese Kyōgen and is usually paired with the female character Okame. Usobuki is often referred to as "the whistler" due to his facial expression of pursed lips.

His countenance is remarkable for its expression of forceful effort and his puffy cheeks, bulging eyes and furrowed brow have been used to portray a wide range of characters within the Kyōgen repertoire. Usobuki masks have been used to depict everything from comical human characters to the spirits of plants, fish and insects, including mosquitoes, mushrooms and even pine resin. Perhaps most remarkable of all is Usobuki's appearance as a sinner on his way to hell in a play entitled "A Sinner with References".

Kyōgen theatre (lit. wild words) is thought to stem from Sarugaku, a form of Chinese entertainment brought to Japan around the 8th century. It was a popular form of entertainment which included such elements as mime, acrobatics and magic encompassing both drama and comedy. By the 14th century, these contradictive forms of Sarugaku had become known as Noh and Kyōgen, respectively.

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