Aka no ori
This is a one-shot chapter from Oshiokiyo! an anthology of hard-yaoi BDSM borderline porn. Featuring a plot about two brothers from a small-time yakuza family whose parents are murdered by a rival family. Older brother becomes just like the enemies in the process of getting his revenge on them. Older brother-younger brother relationship devolves into top/bottom BDSM situation.