Remnants of filth: Yuwu (novel) Tome 4

The wildly popular danmei/Boys'' Love novel series from China set in the universe of Noble-born Mo Xi is the foremost general of Chonghua, known for his ruthless temper and ascetic air. Once he was one of two promising young commanders, twin stars of the empire. His comrade, the lowborn Gu Mang, was Mo Xis brother-in-arms, best friend, and--secretly--his lover, until the day Gu Mang turned traitor and joined the ranks of their nations greatest enemy. Now Gu Mang has been returned to the empire a ruined man, a shadow of the military genius he once was. The public clamors for his death, and no one yearns for vengeance more than Mo Xi. Or so he thought--for faced once more with his bitterest enemy, Mo Xi is left with more questions than answers. Why did the man he loved betray him? And what secrets hide behind Gu Mangs tortured eyes?