W - Two Worlds Apart (2016)

Oh Sung Moo, the father of cardiothoracic surgeon Oh Yeon Joo, mysteriously goes missing while writing the last chapter of his webtoon "W". Yeon Joo goes to his office looking, but a hand from his monitor suddenly pulls her in, and she finds herself on the rooftop of a building, next to a bloodied man. She manages to save the person, only to realize that he is Kang Cheol, the main character of her father's webtoon. Yeon Joo later discovers she can only enter and leave the webtoon depending on Kang Cheol's feelings.

They enter a world of manga / manhwa and live a romance with the protagonist of the story.............

Traveling between worlds
Fl fan of ml
Though divided by separate worlds fl and ml begin a relationship
Fl "marries" ml
Fl partners with ml to save his life

Both of these dramas have two characters who are intricately involved each other through parental ties as well as a mysterious murder case. In both, the leads travel into different dimensions for each other.
In Train, the ML travels into a parallel universe to protect the FL.
In W, the FL travels into the world of comics to save the ML.
Both of these dramas are beautifully shot and while Train does focus more on the murders and W more on romance, they both give extremely similar vibes when it comes from the transition shots from dimension to dimension.

Both have male protagonists that were framed for their family murders and were unjustly imprisoned. They both struggle to bring the truth to light.

Oh Sung Moo, the father of cardiothoracic surgeon Oh Yeon Joo, mysteriously goes missing while writing the last chapter of his webtoon "W". Yeon Joo goes to his office looking, but a hand from his monitor suddenly pulls her in, and she finds herself on the rooftop of a building, next to a bloodied man. She manages to save the person, only to realize that he is Kang Cheol, the main character of her father's webtoon. Yeon Joo later discovers she can only enter and leave the webtoon depending on Kang Cheol's feelings.

Both have FL fall in love with fictional ML. My Dear Warrior has more supporting cast involvement than in W.

Both dramas have a fantasy aspect. In Chicago Typewriter, the way the drama switches back and forth from present- day to the 1930s is similar to how W switches between the real world and manhwa world.

Both have a male and a female lead, which future and past can get re-written. They fight against an invisible opponent, who tries to harm the male lead and do their best to stay at the right time and place and possibly together.

Both dramas have characters from fictional work cross over to the real world to harass the authors into changing their stories.

Two young people meet in a fantasy world in which different rules apply. They often switch from this world to their actual reality. Sometimes that creates problems with their surroundings and puts their family and friends in trouble.

W- two worlds this series also have a parallel world. Though there's an anime artist who's writing everyone's fate. Both are thrilling dramas. Lots of intense but Alice in Borderland still doesn't have any romance but in W it has. Lee Jong Suk is the ML.

In W the male lead is from an other World, and in Hit The Top he is coming from the past.
Though that was just the only similarity. They give absolutely different feels.

Both dramas involve one or more of the main characters from a manga/webtoon world that teleports to the real-life world. These manga/webtoon characters get into a romantic relationship with the real-life character.

Both dramas are about a ML who comes from another world (the past/a manga) to the modern world. In both the FL can influence/change events by writing or drawing them in a book/manga. Both couples have a list of romantic things the FL wants them to do. Both MLs begin to fade away, starting with their hands going transparent/able to pass through things. There is also a villain from the ML's world who ends up in the real/present world.