Train

Though both the dramas have parallel universe sci-fi shit, Train shows more of a thriller showcase than Derailment while the latter shows more romance.
Even the titles are interlinked.
In Derailment, we see the FL trying to find herself but in Train we see ML trying to find a serial killer. Train has a very subtle romance and isnt the main genre.
But both are very captivating.

Suzuri Kanna is married to Suzuri Kakeru. After 15 years of marriage, Kakeru suddenly dies in an accident. Prior to the accident, their marriage was going through difficulties and they were on bad terms with each other. Now, Kanna is about to start her new life. At that time, she obtains a way time travel through time. She travels to the past and she meets young Kakeru, right before she met him for the first time. Seeing the younger Kakeru, she realizes that she loved him and she falls in love with him again. She decides to save him from his death that happens 15 years later.

As their second year of high school begins, Kinoshita Ninako, Ichinose Ren, and Ando Takumi find themselves in the same class. While Ninako is secretly thrilled to be in the same class as Ren, her fantasies are soon interrupted by the arrival of Sugimoto Mao, a younger student who went to the same middle school as Ren and Takumi – and who seems to know a secret about the boys.

As the school year progresses and Ninako learns more about Ren's past, their budding connection begins to falter. At the same time, Takumi begins to express interest in Ninako, leading to tension between himself and Ren. Will Ninako's first love come to fruition?

Yoon Shi Yoon, aka the master of double roles. In Train he plays 2 versions of the same detective with different personalities living in different worlds, while in Psychopath Diary, he plays the role of a timid office worker who believes he is a serial killer and has small bursts of moments where he "becomes" one.

Both shows also revolve around trying to find a serial killer. In Train the story focuses on finding who the killer is, while in Psychopath Diary the story reveals the killer in the first episode.

Psychopath Diary is more a comedic dark mystery, with moments that will make you laugh, while Train is more of a typical strict crime show. Both shows include crumbs of romance, but it is not the overarching focus.

This is about Chihiro, a teenager who has only gone to an all-girls school and has no experience with boys whatsoever. One day, a boy that she sees at the train station every day asks her out and thus she begins her first relationship. This manga portrays the up and downs of first love with a good dose of humor.

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.

As their second year of high school begins, Kinoshita Ninako, Ichinose Ren, and Ando Takumi find themselves in the same class. While Ninako is secretly thrilled to be in the same class as Ren, her fantasies are soon interrupted by the arrival of Sugimoto Mao, a younger student who went to the same middle school as Ren and Takumi – and who seems to know a secret about the boys.

As the school year progresses and Ninako learns more about Ren's past, their budding connection begins to falter. At the same time, Takumi begins to express interest in Ninako, leading to tension between himself and Ren. Will Ninako's first love come to fruition?

- 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.