Ai no Kusabi (間の楔) is a Japanese novel written by Reiko Yoshihara. Originally serialized in the yaoi magazine Shousetsu June between December 1986 and October 1987, the story was collected into a hardbound novel that was released in Japan in 1990. This futuristic tale is set in a world where the Elites are assigned various social classes based on their hair color in the city of Tanagura. Iason Mink, a high-class "Blondie", runs into Riki, a black-haired "Mongrel", and makes him his "Pet", which Riki resents being. As Riki learns of the dangers Iason faces by keeping him, he finds himself developing feelings for his master. Focusing on the relationship between Iason and Riki, Ai no Kusabi also explores issues of caste systems and social exclusion.