Same genre as Signal but this one is miles better in terms of detective work, logic and acting (although i still love Lee Je Hoon). Here the time travel is not what solves the cases. The characters are actually good detectives. Time travel is just an explanation for the existence of one character. The cases all contribute to the main plot but are just as intriguing individually. And of course the characters really choose to walk by themselves in dark alleys and fields. This is common in korean crime dramas.