In Victorian London, a stormy night, Sil Vandom Hewi welcomed his tenth birthday.However, a sudden fire swallowed his manor and took the lives of his parents.While wandering on the verge of life and death, the young Schill made a contract with a demon - at the cost of his soul in exchange for the power of revenge.The demon has since become his loyal servant, calling himself "Sebastian Michelis", and vowing to protect and serve allegiance to Schill until the contract is completed. A month after the fire, Schill, who had just disappeared for a while, returned to the world with the mysterious new housekeeper.Despite his young age, he has inherited the family business and became the helm of Vandom Havi's business, shouldering the burden of the family business empire.At the same time, he also undertakes the "watchdog" mission entrusted by the Queen of England, secretly pursuing the truth and finding the murderer who killed his parents.In this city where light and shadow intertwined, Schill put on the cloak of indifference and walked step by step into the abyss of revenge.