Ai no Kusabi (Wedge of Interval) is a novel written by Rieko Yoshihara. The story ran as series on a famous Japanese shounen ai magazine, Shousetsu June (No.22 December 1986 to No.27 October 1987). The story then was slightly reedited by the author and has been published as a hard-cover book since 1990. (The novel is in Japanese and only in Japanese).
The story combines science fiction, aestheticism and yaoi. Ai no Kusabi focuses on the love and conflict between 3 main characters, Iason Mink, Riki and Guy. The background takes place in a future computer-controled society, Tanagura, where people are divided into different ranks that are based on their hair colors. This is hentai, yaoi.