Here are 4 Detective/Investigation drama's you should you check out if you're a K-Drama fan!
These drama's may fit into other genre's as well!
Also these are all from the collection of drama's I've seen.
Main Cast: Lee Je Hoon, Kim Hye Soo, and Jo Jin Woong
"After finding an old walkie-talkie, Detective Park Hae Yeong manages to connect with Detective Lee Jae Han in the past. Together, with the help of Team Leader Cha So Hyun, they manage to solve South Korea's most famous cold cases and reveal police corruption."
2. Lookout/ The Guardians
Episodes: 32 (30 minute episodes)
Main Cast: Lee Shi Young, Kim Young Kwang, Kim Tae Hoon, Kim Seul Gi, and Key(of SHINee)
"Story about a group of people who get together to overcome their pain of having lost their loved ones to crime."
Main Cast: Yang Se Jong, Jung Jae Young, Kim Jung Eun, and Seo Eun Soo
"Jang Deuk Cheon is the chief of a crime squad. At home, he is a kind and friendly father to his daughter. He meets a human clone and gets involved in a shocking case. A battle takes place between human clones."
Main Cast: Choi Jin Hyuk, Yoon Hyun Min, and Lee Yoo Young
(And I shamelessly have to add in that Cha Hak Yeon of VIXX is in this drama as well!)
"In 1986, Park Gwang Ho works as an excellent and enthusiastic detective. His life changes when he’s pursuing leads in a serial homicide case and then passes through a time portal, which transports him to present day Seoul. He meets a new partner Kim Sun Jae, an elite detective who happens to be a bit eccentric, but is one highly skilled investigator. The detective duo will also find help in psychology professor, Shin Jae Yi."