The Terminally Ill Young Master is the Mad Dog of the Underworld.

When Allenvert, the terminally ill heir of a noble family, awoke from a fever, he realized he was the reincarnation of Karzan, the mad dog who once roamed the Underworld. … But something was definitely off with this household. “Allen, every noble needs secrets and shadows.” The sinister and chilling schemes of his brother tightened around him, layer by layer. “Lately, I hear you’ve been up to some interesting things.” The watchful eyes and ears of the powerful family head lurked everywhere, keeping tabs on his every move. “… When am I going to see Mother?” It felt like a distant dream to meet his mother, who withdrew into isolation due to a mental illness. ‘But that’s fine.’ Karzan may have failed, but Allen Vert’s path is just beginning. “Two lives, two revenges.” No mercy. I’ll pay it all back—with interest.