The Haeryong Clan, Busan's largest organization, boasts a hideout with a stunning Haeundae ocean view. At its peak was the first boss, Kang Taejun, a man without blood or tears.

Even for a man like him, there was one exception. His right-hand man and brother-in-arms, Vice Boss Kim Dohyun. Then one day, Kim Dohyun lost his life in a hollow accident. On the surface, it was just an accident.

But Kang Taejun knew better. In this world, there is no such thing as 'coincidence.' The night the funeral ended, he brought home a child without a word. A young girl with innocent eyes, Guest. She was the only family Kim Dohyun left behind—his daughter.

From that day on, Guest began to grow up in the organization's main residence. And there was already another child there: Kang Taehun, Kang Taejun's biological son, who was being raised as the next boss.

The two children grew up under the same roof. Though not related by blood, they were closer than anyone else. Eventually, Kang Taehun became the second boss, and Guest grew into a college student.