Train

The base concept is different. In tunnel it's about time travel, while in Train, it's about traveling between alternate realities. Even so, there are numerous similarities, which you'll recognize if you watch both shows.

Overall, it's a mysterious show that stays interesting throughout.

Holy shit how is this drama so underrated?? It has a fantastic script, characters, actors, soundtrack, filming etc. I really enjoyed this. It's probably one of my favourite sci-fi/crime kdramas. Excellent acting form Yoon Siyoon also. Wooowwwwww. Don't give this one a miss. That's all I can say.

This was one of the first KDrama's I have watched while it aired, and let me just say that every episode kept me on the edge of my seat, and I was SO disappointed having to wait each week for the next two episodes! Yoon Shi Yoon is quickly becoming a favorite actor of mine; he has quite the range and this really showed when playing the two different versions of the Seo Do Won. He had a similar acting experience in "Your Honor," where he played twin brothers, but this show and these characters were much better in my opinion. The plot is complex but well paced and understandable, and much better done than "The King: Eternal Monarch" which had a similar premise but was executed in a much more confusing manner. This is also one of the first KDrama's that I have watched that hints at/needs a second season - very badly! Overall this was a very enjoyable watch with great acting, well developed characters, and an addictive plot.

I really enjoyed this series, the acting and script is first rate... I have enjoyed all the time travel Korean shows but this one is the best, maybe cause it's 12 episodes only... The lead actors are superb and I have watched now about 25 plus Korean dramas and this us definitely near the top with Mr Sunshine, Misaeng, Heachi and Stranger. Definitely recommended this series

I must admit that I was confused during the first five or so episodes but was intrigued enough to stay with it.

I am happy I did because the story began to unravel and make sense after that. Much suspension of disbelief is required but then again, this is a sci fi/fantasy show so a lot of creative license was used.

Actors turned in good performances. I last saw the female lead as half of the second couple in Weightlifting Kim Bok-joo. Male lead in this show was very convincing as good cop/bad cop. This show is recommendable to those who love suspense, crime, whodunnit shows.

12 episodes were well-utilized. The team thought well enough not to force 16 episodes out if this.