One day, Lee Taeyang, a young and handsome detective in the Seoul Police Department, has just been given a tough new assignment. Despite his young age, he is already known as a talented detective with exceptional martial arts skills. He was appointed to handle a very difficult case that no one has ever managed to solve.

The case involves a series of mysterious murders that have terrified the citizens of Seoul. Despite numerous reports and investigations, the culprit always manages to disappear without a trace. The killer is very cunning, always tricking investigators and leaving little evidence.

On a cold night, Taeyang received a report that there was another murder in an apartment located in a fairly crowded area. Once on the scene, Taeyang sensed that something was different about this case. With a keen sense, he checked the surroundings and immediately knew that this wasn't just another murder. There was a very neat and mysterious pattern, as if the perpetrator was waiting to be caught.

With his advanced martial arts skills, Taeyang didn't just rely on his brain to solve this case. He has to deal with challenging situations, meet secretive people, and solve puzzles that have plagued many detectives before him. However, the deeper he delves, the darker and more complicated the case becomes. In fact, he begins to feel threats from unknown parties who are trying to stop his investigation.

The night was getting late, and the temperature outside was getting skin-piercing. Lee Taeyang stood in front of the apartment door, feeling the tension coursing through his body. The dim street lights gave the neighborhood a gloomy feel. He looked around, feeling that something was wrong. When the apartment door opened, a strong smell of fishy odor greeted him.

After entering the neat-looking but dark apartment unit, Taeyang looked carefully at every corner of the room. The victim's body was lying on the floor, with very precise wounds. There were no screams, no signs of resistance. It was a familiar method, but still, different. He knew the culprit was highly trained.

"This is no ordinary murder," Taeyang muttered, his eyes scrutinizing every detail. Soon, he noticed a message hidden behind the glass of the desk. A strange number was written in red ink, as if giving a clue, but also complicating the situation.

Carefully, Taeyang grabbed his cell phone and called his colleagues in the police force to secure the place immediately. He knew this would be a very complicated case and could be dangerous for him. While waiting for the arrival of the forensics team, he thought hard. "What does this number have to do with previous cases?"

A feeling of unease began to overcome him. There was something bigger than just this murder. A well-planned death, and a pattern that suggested that this might just be the beginning of something much darker.

Taeyang took a deep breath. This was his biggest test as a detective. He had to tread carefully, probe deeper, and uncover who was behind all of this, before it was too late.