Synopsis：Underground fighter Ethan is forced to become ruthless mob boss Leon’s “collateral” to save his sister. Though cold and merciless on the surface, Leon secretly shields Ethan and his family and personally trains him to grow stronger. Misreading Leon’s protection of his sister as a betrayal, Ethan is manipulated by police mole Noah into plotting Leon’s assassination. At the decisive moment, Leon takes a bullet for Ethan, exposing Noah’s true identity. With the misunderstanding cleared, Ethan and Leon join forces to destroy their common enemy Victor and legitimize the empire. From sworn enemies to devoted lovers, they become each other’s only cure and inevitable destiny.