Ai no Kusabi (間の楔, Ai no Kusabi) is a Japanese novel written by Rieko 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 men are assigned various social classes based on their hair color. Iason Mink, a high-class Blondie, runs into Riki, a black-haired Mongrel, and makes him his "Pet." As Riki learns of the dangers Iason faces by keeping him, he finds himself developing feelings for his master. Focusing on the ill-fated love between Iason and Riki, 'Ai no Kusabi also explores issues of caste systems and social exclusion.