Imagine waking up to a life that is both familiar and terrifyingly new. In *The Terminally Ill Young Master is the Mad Dog of the Underworld*, Allen Vert, a young noble burdened by a fatal illness, discovers a shocking truth: he is the reincarnation of Karzan, a notorious figure from the Underworld's dark history. But Allen's second chance is far from simple. His noble family, cloaked in secrets and shadowed by ambition, presents a treacherous landscape. A brother, all smiles and veiled threats, tightens his grip with layers of sinister plots. The family head, a figure of immense power, watches Allen's every move, his eyes and ears permeating the household. And somewhere within the estate's walls lives his mother, a broken spirit lost in seclusion, a distant beacon of hope for Allen. Fueled by the memories of Karzan's past failures and the injustices of his present, Allen embraces his dual existence. He vows to navigate the intricate web of noble intrigue and exact a ruthless revenge. This is a story of second chances and merciless retribution, of a terminally ill young master wielding the ferocity of the Underworld's mad dog. Allen Vert's journey has only just begun, and he intends to make them all pay—with interest. Will he succeed, or will the shadows of his family consume him?