Recommendations

you should watch TBNW first as the other one is a special extra epsisode with a light story, fluffy, some kissing and a bit fan-service, there isn't anything surprising but still, it is cute overall, with the same good chemistry between the actors :)

‘Accidental’ marriage/marriage of convenience
(Very loosely used here)

He fell first but she fell harder.

Have some time of history before ‘first’ meeting.

Very cutesy scenes.

Dan Bi is a high school senior who has given up on math. On the day she is about to take the KSAT for college, she is transported back into the past during a freak rain shower. She finds herself hundreds of years in the past at the height of the Joseon Kingdom, which is suffering from a severe drought. She encounters King Lee Do who yearns to learn advanced mathematics and falls in love with him. This is a romance that transcends space and time with two lovers who come to know each other on a deeper level.

Crown Prince Yi Gak finds that he has been transported from the Joseon Dynasty to modern-day Seoul. He meets Hong Se Na, who bears a striking resemblance to his dead wife, and is determined to solve the 300-year-old mystery of her death. With his own resemblance to the CEO’s grandson at the company where Se Na works, Gak assumes the identity of the young man to stay close to her. Can the Crown Prince navigate a modern corporation to find clues to his own time period

Ma Gwang Suk works as a section chief at the Shiwan Post Office. She is 45 years old and single. She meets O Jang Su, who is CEO of Eagle Brewery, and they decide to get married. But, only 10 days after their marriage, O Jang Su gets into an accident and dies. Ma Gwang Suk takes over the brewery and becomes the breadwinner for her 4 younger brothers-in-law. She has a cheerful and lively personality, which helps her persevere.

Han Dong Seok is the chairman of LX Hotel. He was born into a wealthy family and has never lacked anything, but having lost his wife 15 years ago, he lives his life in loneliness. He is also arrogant and has a clear opinion on what he thinks is right or wrong. He meets Ma Gwang Suk.

This is for the special edition, the same story and the same exact cast, and this is for the extra- Due to an unforeseen situation, a naive freshman and the campus’s popular senior agree to pretend to be a couple—but their fake deal begins to affect their real feelings.

Is the uncovers, same story. Due to an unforeseen situation, a naive freshman and the campus’s popular senior agree to pretend to be a couple—but their fake deal begins to affect their real feelings.

Both dramas tell stories about complicated relationships. "My Dearest Nemesis" seems to be about people getting over bad things that happened to them and growing as people. "My Sweet Mobster" seems to be about a man trying to be good after being bad. So, if you like shows with people who have old relationships and change a lot, or if you like shows about childhood relationship, you might like both of these dramas.

Both dramas have FLs who are smart, business-savvy women in the male-dominated steel industry of 1980s China. Family-friendly dramas. Both excellent.

Similar era—1980s. Both stories show the development of the leads from their humble status to business leaders.

Both dramas are great makjang, complete with birth secrets, angst, murder plots, and revenge. One difference is Hotel King has more romance, but the revenge plot is still the driving force of the story.

High school students mysteriously isolated/separated from society.
Romance subplots amongst the overarching sci-fi themes.

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Both of these dramas are BLs about students coming of age and falling in love. In both of these dramas one of the leads has an abusive father. And both feature a delicious serving of angst. There is even more similarities but those would be a big spoiler, so just watch for yourself ;-)

Both dramas are about reincarnation in multiple lifes and the biggest question is if the protagonists will solve the problem that caused all the reincarnation thing. Another similar thing is that they retain the memories of past lifes.

The difference is that "See you in my 19th life" focus more in the last and current life of protagonist while in "Death's Game" we go through all protagoist's lifes after his main death.