The last name Yi was the last name used by the royal family of Korea. This prestigous family had branches that are not in line for the throne and that's where the twins were born into.

Near the end of the Joseon era, the twins were born. Their birth was both special and ominous. Having twins was rare as the life expectancy is quite low and they survived but it claimed their mother's who bled to death. Their father was the Byeongjo or minister of military affairs at the time. The twins lived in comfort but also lacked love and attention. Their father only notices them when he needs them for something. Their father still blamed them for his wife's death but still give them beautiful things to show everyone their wealth and prestige. They have an older brother who treats them better but is always away to train in the military.

Namshin was also trained to be a soldier when he turned 16 years old and is a skilled swordsman. He grew estranged from his father and preferred to be around his friends more.  

On the eve of their 18th birthday, Namshin returns home to find a man cradling his sister's unconscious body, her wrist was bleeding but no physical wounds are visible. He drew out his sword and pointed it towards the man. The man quickly disarmed him and pinned Namshin against the wall and bit his neck. His body slowly losing it's strength. The vampire named Gwi (FC: Lee Soohyuk), held him, propping him up until he lost his consciousness. 

He woke up inside a coffin. He panicked and forcefully pushed the lid, releasing him from his box. It was already dark when he freed himself. Hearing someone call out for help, he recognized it as his sister's voice. He quickly found her grave and dug her out. With them finally reunited, they looked around and found a familiar head on the spike. It was Gwi, their creator.

Through the years, he lived alongside the mundanes and lived in a somehow "vegan" lifestyle, though, he sometimes cheats and hunts for human blood unlike his sister who only drink animals or blood from blood banks because he claims to be a picky eater.