Train (2020)

Although the story lines aren’t similar, the concept of transportation system (a train in Train and the subway in Catch the Ghost) is what the mystery in both dramas are based on. The killers in both dramas have a similar strategy in murders too, both having to do with suitcases...

The tone of the drama is similar. Few words are repeatedly used by the main leads in all the episodes. Both dramas doesn't proceed in the way you expect it to be.

gripping, complex & full of dark and futuristic themes, both of these dramas are absolute must-watches, particularly if you want to watch something special & unlike many other dramas
>> the execution of the dimension-switching in train is highly convincing, plus very reminiscent of the divided timelines in circle
>> similar overall vibes (although train is more supernatural? vs circle's scifi)
>> both focus heavily on investigations
>> the male leads suffer traumatic losses, dedicate their lives to protecting their loved ones & uncover some nasty truths along the way
>> ...with a side of thought-provoking (and often mind-blowing) moral/ethical issues caused by messing with fate (train) and memories (circle), and how these can butterfly effect to drastic proportions.

The scene that appears at the beginning of the series is similar. Those trying to convey the drama look alike. Even if they are of different types. But also different lives and choices, and the events that result from them are very similar.

- doppelganger identity switch as both are from time travel and the good/evil impersonate like the other one
- plenty of twists, thriller & every episode will keep you on the edge of what happens next

In both the protagonist works as police officer and suffers from discrimination, because his father is convicted for murder.