Faith

The two stories take place in the same historical time. Faith takes place in the last part of Empress Ki, after she gets married.
While in Goryeo reigned King Gongmin and Queen Noguk (Faith), in Yuan did Emperor Huizong and Empress Ki (Empress Ki).
The two states were in constant conflict with each other. In Faith, King Gongmin had to fight against those who wanted Goryeo to be another province of Yuan. And one of those, was the main antagonist, Ki Cheol, brother of Empress Ki.
Both are historical, action and romance dramas. Only that Faith it's a lot lighter, have fantasy and medical themes, and focused in a romance story between two characters. Empress Ki is a darker and more serious story, with lots of tragedies and political themes, that focuses on a longer range of time, and in which the romance is just another one of the many points that has to offered.

Both saeguks with beautiful romances and palace intrigues that were really not that difficult to follow. Plus LMH and KSH. You're welcome.

So, I recommend Shin Don only because it has common historic characters with Faith. You'd watch it if you have educational purposes (want to learn more about the period).

Both are historical dramas with political intrigue, romance and magic.

Both are time traveling dramas. :DDDD

Both dramas have same concept : Time travel, historical. On them both characters will live a sweet love story

University student K is an ordinary young woman, but, one day, she finds herself in her favorite romance novel set during historical times. She has now become the minor character Cha Seon Chaek. She is the daughter of a wealthy noble family and her dream is to have a peaceful and normal life. Cha Seon Chaek, while possessed by K, then spends one night with Lee Beon, the lead male character in the novel.

He comes from a royal lineage and is favored by the King. Lee Beon has a cold-blooded personality and is gifted with an attractive appearance and outstanding martial arts skills. He has also experienced a heartbreaking past. Somehow, Lee Beon and Cha Seon Chaek happen to meet and talk. Lee Beon is consoled by her about his heartbreaking past. They spend the night together. Soon, Cha Seon Chaek tries to connect Lee Beon to Cho Eun Ae, who is the lead female character in the novel. According to the novel, Lee Beon and Jo Eun Ae are supposed to fall in love, but, due to the appearance of Cha Seon Chaek, Cho Eun Ae's fate has changed. No matter how hard Cha Seon Chaek tries, Lee Beon’s love always finds its way back to her.

Other people around them include Jung Su Gyeom and Do Hwa Sun. Jung Su Gyeom is a young officer from a prestigious family. He is Lee Beon’s only friend. Do Hwa Sun is an ambitious woman whose life goal is to marry Lee Beon and become a member of the royal family.

In both dramas, the couple is balanced, they love and sacrifice unconditionally
There is no love triangle, nor nagging female
Male lead falls first in love
Between country and love, both ML will put first their love
Both have happy ending

"A modern-day surgeon is kidnapped and taken back 700 years to the Goryeo Dynasty in Korean history."

Time-traveling and doctors that change the fate of the past.

They are both set in the Joseon era
They are both dramas worth watching.. if you liked one then you should definitely have a go at watching the other.

Although Vigilantes in Masks is not supernatural/ time travel inclined the filming style, animation included, and the seemingly laid back attitude of the male character reminds me of Faith's.

Both are fantasy dramas and faith has Lee Min Ho :) You get to see time travel and it is a good story.

All the gods will be leaving before the last rain of doomsday. However, an ordinary human girl unexpectedly puts a dent in their plans to retreat thus causing the world to move towards the unknown. Based on the animistic mythology of the Amis tribe, the gods are no longer willing to bless the land that is plagued with environmental issues. One by one, the gods depart the world they once loved. A human girl discovers that the opportunity to reverse her destiny lies within herself and her guardian. Before the final day of judgment, a love story between human and god unfolds.

Both female leads are doctors with similar personality types. They both get transported to another realm/time period. While Faith is more of a medical drama and sageuk, W is more of a modern day romantic comedy.