The Scholar Who Walks the Night

This drama is a love story between Kataoka Sakuya, a grim reaper who comes to the human world for the first time, and Mochizuki Nayuki, a woman who lost her father at a young age and has devoted her life to raising her only remaining family—her younger brother. As they meet, they gradually come to understand each other, and slowly, they begin to fall in love. However, a fate that will dramatically change their lives awaits them both…

Scholar Who Walks The Night and The Emperor: Owner of the mask have similarities. Both story is developing the crown prince to become a great King.

It's because there is a cruel person/vampire that stand behind the Kings order and the Prince were forced to serve that person/vampire in order to keep his people save.

In The Emperor: Owner of The Mask there is Daemok. In Scholar Who Walks The Night there is a vampire called Gwi.

L, an angel who’s endlessly fascinated with the human world, gets into trouble when she unthinkingly saves the life of Han Shi Yeong, a man who was meant to die. To make up for her mistake she must guard him on Earth for one hundred days and keep him safe from Hwan, a death god who is required to collect his soul. Both supernatural beings must contend with the knowledge that whichever one of them fails by the end of the hundred days will be erased from existence, and the longer they stay on Earth the further their powers fade and the more human they become.

Both are historical dramas in which the ML is turned into a vampire and later on meets the human FL.

Yamihara Kokoro and Asada Toramatsu live in a town that is quite peaceful, until a serial murder case happened where the bodies all had their blood drained out. Five years have passed but the case remains unsolved. Meanwhile, Kokoro and Toramatsu have been in a relationship for a year, but are unable to get married as they are keeping a serious secret from each other. Kokoro is actually a vampire. However, she does not attack humans and live modestly. Toramatsu is a popular resident in the town and is trusted by many. After getting a divorce, Toramatsu got drunk and went back to his old house, where he met Kokoro, the current occupant. As the two continue to keep their secrets hidden, a horrific murder occurs once again in the town.

Comedic film of a fusion-historical genre. Cute lover boy Heo Saek becomes Joseon's first male gisaeng and a flower-like woman named Hae Won who thinks ahead of her time, search for true love together.

Lee Joon-gi in another period piece doing what he does best by bringing the titular lead to life.

Park Yoon-kang is the son of the last great swordsman of the 19th Century Joseon. After the murder of his father and the enslavement of his younger sister, Yoon-kang trades his sword for a Western rifle on a revenge mission to find his sister and those responsible for destroying his life , but he ends up becoming a hero for the people as he fights corruption and his own inner demons.

Lots of action and romance with strong characters both male and female.

=> We see in Scholar Walks at Night episode 17 that Lee Joon Gi acts as 3 characters meeting. In Arthdal, fans are waiting for Eunseom Saya meeting. You can use LJG Scholar Walks at Night scene to see how he will act the meeting scene of Eunseom and Saya in Arthdal.

Mermaid Got Married is the Splash-like tale of a beautiful mermaid who loses her pearl when she saves high school teacher Dior Cheng from drowning. It turns out she also saved him when they were both kids so there's an immediate connection between the two. Unfortunately, the pearl is the source of her power so she follows him onto land.

Lee SooHyuk is also a vampire in this story. Where Vampire idol is a comedy, Scholar is a darker heavier program that should be watched by all who love Vampires.

Scholar Who Walks the Night is one of my favorite dramas. It has many supernatural twists. Mirror of the Witch is about witchcraft and SWWTN is about vampires. Both ways, both are Sageuks in the "dark". If you love this drama, give Scholar Who Walks the Night a try!

It focuses on a naive, loudmouthed teenager named Rion, who investigates a host club full of vampires when she suspects they must be related to the disappearance of a lot of people in the neighborhood, including her best friend. In the process she begins to befriend them, especially the leader Suou, with whom she develops a romantic relationship. Ultimately, she figures out the vampires are not the cause of the disappearances, but her adventures with the vampires are only beginning

Another historical drama about the corruption of power. Also, they are both about the strength of the people, good over bad, and the struggle for justice.
I find that even though the plot lines may be different, one being about a princess and one about a vampire, they have very similar characters and character relationships.

The female lead in both dresses up as a male, for their survival, in the early part of the drama. They are both bright and friendly, though, Jo Yang Sun isn't as thoughtful and clever as Jeong Myeong. Both have a strong fate with the inner workings of the palace.
Both male leads are kind and caring, and will go to the lengths to protect their leading ladies. Their caring love is what makes you heart race while watching the drama. Difference though, Kim Sung Yeol is a vampire and Hong Joo Won is a bashful scholar (well he moves up in rank through out the drama) .

The royals in the drama are similar too, where, as much as they want to fight the corruption, its extremely difficult. In the process, they lose their original goal and stray. Their mission throughout is continuously remind themselves of purpose and try to find the right retainers.