She was four when they send her away . One misunderstanding. One signature. And her entire existence was cut clean from the family record. China became a holding cell. A hostel with hidden walls. That place swallowed children whole. Those who broke were buried. Those who survived... learned to kill. Yihun became one of the survivors. Raised by the underground syndicates of Europe, she sharpened into a weapon built of cold precision, selfish ambition, and a rage that never slept. She killed for money. She killed because it was the only language she was allowed to learn. Revenge became oxygen. So when they gave her the ultimate contract - assassinate the most powerful mafia lord in Asia - she said yes without hesitation. She didn't know she shared his blood. Kim Namjoon. Her brother. Twelve years lost between them. Just when the kill was in her scope... everything twisted. A deal with the police. A new mission. A new hell. She must infiltrate their world as a spy - living under the same roof as the family that abandoned her - appearing like a normal girl while carrying the scars of a trained predator. But in this empire, trust does not exist. And every smile hides a blade. This is a story about blood, betrayal and the kind of darkness that never lets you sleep. A BTS brothers mafia universe. Cover by user_thv.