Mask (2015)

Both have female twins that haven't met each other until they were adults, the poor twin lead the rich twin's life for different reasons.

But in Bride of the Century, there is a supernatural element; while Mask does not.

As I was watching Mask, I kept thinking it's kind of like Secret. Then I found it's from the same writer. The main thing about both is the evil guy is really evil.

Both main girl’s take on different identities. The main girl in both struggle with their new identities.

This drama is a delicious combination of City Hunter + Healer + Mask + Descendants of The Sun
It has a military plot as DOTS, but with a darker atmosphere. It has the same political and bodyguard theme as City Hunter. Healer comes to this mix because the male lead is the same, and he have to hide his identity.
I also put Mask here bacause it has a similar feeling around the girl in K2 and the male lead in Mask, both from important/rich families that have to hide thenselves or they true selves from public image.
Very good drama! The action is insane and the male lead is superb in his acting, the cast is very very good!
Hope you enjoy as much as I am!

Both dramas involve the FL living another person's life (in Mask while being a doppelganger and in 49 Days by possessing a body). I feel like the melodrama aspects of them are somewhat similar as well.

Shin Ji Hyun was enjoying absolute bliss as she was about to marry her fiancé, Kang Min Ho, but her perfect life is shattered when she gets into a car accident that leaves her in a coma. She is given a second chance at life by a person called The Scheduler, but it comes with a condition: she has to find three people outside of her family who would cry genuine tears for her. In order to do this, she borrows the body of Yi Kyung, a part-time employee at a convenience store for 49 days.

really similar plotline
doppleganger
rich household and want to acquire money
fl forced to play the dead person
melodrama

Both are introduced as melodrama and makjang which revolve around "identity swap" as the overarching theme. In Mask, it involves two strangers who look exactly alike (doppelganger) while in Nice Witch, it involves an identical twins.

Due to certain circumstances, both main female leads (who also happen to be the ones living a hard life and currently in a dire situation), were asked to take the other's identity and later became entangled with powerful people and series of misunderstandings.

Compare to Mask, Nice Witch has more comedic values in it.

Both Dramas have the same dark vibe and start with someone drowning under similar circumstances. In both cases the female lead has a connection with the deceased person and the male lead with the "killer".

Another case of identity swap! A guy falls in love with a girl whom he thinks is someone else. Things happen which make him wonder but he never suspects the change in identity.

When Shiho Nishina got worried about her sex life with her husband, her husband proposed to her, "Why don't we go to a couple exchange party?" At first Shiho strongly turned down the idea, but eventually, she gave in because her husband was very persuasive. "We're just going to observe, okay?" Shiho said as she reluctantly agreed to it. Meanwhile, a former diplomat Mr. Kubozuka ran a couple exchange club, "Aquarium," with his wife in their house. At first, Shiho was being very cautious, but gradually, she got attracted to Mr. and Mrs. Kubozuka's charm and finally agreed to exchange couples with them. It seemed that their sex problem had disappeard and they had found happiness, but as it turned out, that was just the beginning of their nightmare...

~~ Adapted from the manga series "Fuufu Enman Recipe: Soredemo Otto wo Aishite Iru" by Koshikawa Tamae and Aoisei

Both makjang series that deal with marriage, betrayal, secrets and lies. Both have a character that wears a mask, keeps a secret. But one is male, while the other is female. Only recommended for mature audience.

I recommend this both drama because , Male lead and Female lead
try to solve problem
In one drama explosion and another student murder/suicide

Soma Yui and Torino Naoki were childhood friends, but they met again as adults. Just as he decides to propose to Yui, Naoki suddenly disappears from Yui's sight after being embroiled in a mysterious incident. Naoki continues to wander in this world as a spirit without knowing that he has died.

Naoki asks Uozumi Yuzuru, a detective who is the only one able to see Naoki, to convey his feelings to Yui, but Naoki ends up breaking up without properly saying "thank you, goodbye, and I love you" to the person he loves the most.

Both dramas are about a person being replaced by other of the same appearance but with a really different personality.