Midare Somenishi(1999)

Set in ancient Japan, involving many explicit steamy sex scenes. Shirou and his little brother are captured by bandits, and he is given two options: become the leader's sex toy, or watch his brother die. (And just wait 'til his brother grows up...sexy boy...) Unlike some other hardcore yaoi, this story *does* have a plot and can be rather sweet and sad at certain moments.