Black Out

This is a love story in the guise of a serial killer K-drama. The show is about Seo Do-Won’s (Yoon) who loses the love of his life to an act of crime by a serial killer. He gets a chance to travel in a parallel universe where his girl is, in fact, alive. He tries to catch the killer in the parallel universe.

What happens if a common man accidentally finds a serial killer’s diary? Yook Dong-sik (Yoon), on losing his job, tries to end his life. However, in doing so, he somehow stumbles upon a crime scene. While fleeing the murderer, he is hit and finds the culprit’s diary in his possession. Unable to remember the events before the incident, Yook begins to believe that he is a serial killer, but the real culprit is hiding and hunting for his diary.

This true crime serial killer drama is interesting because it is based on a book by South Korea’s number one criminal profiler Kwon Il Yong and journalist Ko Na Mu. Disturbingly real and suspenseful, this series analyses the psyche of serial killers.

Jang Tae San works at a pawn shop by day and prostitutes himself to older women at night. One day, he's contacted by his ex-girlfriend that he is the father of her daughter with leukemia, and he's the last chance to donate bone marrow and save their daughter's life. That same day, he finds himself framed for murder but manages to escape and runs away. With nobody to trust, Jang Tae San has two weeks to try to prove his innocence and survive until his daughter's surgery.
Park Jae Kyung is a prosecutor searching for evidence to take down Moon Il Suk, the man who stabbed her father, and Jo Seo Hee, a beloved senator who is actually working with Moon Il Suk. Together with Detective Im Seung Woo, she works to uncover the truth behind the murder and its connections to Moon Il Suk and Jo Seo Hee

After the death of an unknown uncle, a woman inherits a burial ground and finds herself in the center of a string of murders and dark secrets.

Both the dramas have same kind of suspense reveal.
In both dramas, incident happens around a group of high school friends in the past which gets solved in the present.

You suspect everyone till the end. All of them are suspicious and hiding something. You can only trust the two main leads ie. In connection there is ML and FL while in black out it is two MLs. ML in connection is Jisung afterall so i dont think I have to explain the level of acting.

has comedic moments but main lead was framed and sent to prison - once out seeks to find who murdered his best friend

The way of filming in Black Out reminds me of Gap Dong.
Both series are about a series of murders of girls in a small town.
Both series have a detective who is hell-bent on finding out the truth of a case that happened nearly 20 years ago.
Both series have a lot of unexpected plot twists and at times twist things every two seconds.

Dog Mask's identity is unknown. When heinous criminals avoid punishment from the law, all citizens over 18 years old receive a text message polling them on whether that person should receive the death penalty. If more than 50% respond in favor of the death penalty, that person is killed by Dog Mask. Meanwhile, the police chase after Dog Mask and three people become involved.

One day, a dead body is found at an apartment near the supermarket. Finding this murder odd, Dae-sung, his mother, and his girlfriend Ah-hee gather around to find the real murderer, starting by looking through the receipts of the market.

A fun-loving rich chaebol gets entangled in an incident and joins a violent crime investigation team. By mobilizing his wealth and personal connections, the third-generation chaebol catches criminals beyond the reach of police.

Do Bae-Man became a military prosecutor to find success and wealth. His job is just a means for him to find success and he looks forward to quitting his job as a military prosecutor.

Cha Woo-In comes from a wealthy chaebol family and she works as rookie military prosecutor. She is confident and does not fear powerful people. She has excellent investigation skills for someone her age. Cha Woo-In also became a military prosecutor to seek revenge.

Do Bae-Man & Cha Woo-In begin to work together as they break down evils in the military. During this time, Do Bae-Man grows into a real military prosecutor.

Gil Soo-Hyun after graduating Harvard University worked at the FBI for 10 years. Afterwards, he decided to come back to South Korea. He now works as the leader of the Special Missing Persons Unit investigating mysterious case of serial killer.

Baek Beom has worked as a forensic doctor for 10 years. He is excellent at his work but does not open his mind to other people. Eun Sol is a rookie prosecutor with a bright personality, and she comes from a wealthy family. The forensic scientist with a bad personality and a warm-hearted prosecutor must join forces in order to catch a serial killer.

Baek Beom, a forensic doctor, collaborates with a newly appointed prosecutor, Eun Sol, to solve peculiar murder mysteries. They overcome their mutual dislike for each other to form a strong team.