The plots are similar where the former lovers are destined to reunite after many reincarnations. Also the fated lovers turn out to be of the same gender.

"Doujin Artist Nekoyashiki-Kun's Desire for Recognition Grows" is similar to "Oh! My Assistant" where Issae Kazama, a Jpop idol, is not only high school classmate but he is also a fan of Mamoru Nekoyashiki's drawings. It's just like Mu Yeong is Seon's fan.

I've not seen the The Love of Winter, but the trailer looks similar to Present Perfect movie. Both case have a heartbroken person getting away to heal his heart. Then he fell in love during the getaway.

Two strangers meet at a get-away-resort. Fate has them as next door neighbor which allows them to get to know each other and fast becoming friends then turn into lovers.

The main leads in these series checked-in the resort to heal their broken heart. Somehow, their rooms are next to each other allowing them to get to know more about the other. They have a romantic encounter there at the resort.

Childhood friends meet years after growing apart. The middle school girl spent time with her crush's younger brother who's in primary school at the time. The boy taking a liking to her till she got engaged and moved to the US. Now,he has grown into a fine man and on equal footing finally get to court his childhood crush.

This a prequel which could be watched before or after His (2020). Both of this could be a stand alone feature. However, I recommend them as to familiarize with the characters.

The young protagonists in these two drama have dream of becoming a dancer on stage. They both have talent stem from their mothers who were once dance in ballet professionally. The young men also have difficulty pursuing their dream due to finances. Also, both young men encounter elderly who helped them achieve the goal.

An old and aging uncle has a second chance for romance. He went into a mysterious photography studio to have his picture taken and left the studio looking decades younger. His younger self met a director of a modeling agency and fell in love.

I've chosen Love Online: Extra (2017) being similar to One in a Hundred drama series because of the bromance between the main leads. Living together in luxury condo has lead the public into believing they are lovers. Also, both stories have one lead as an idol in the entertainment industries.

The similarity of these two is the secret love of an assassin. Long Time No See is about two assassins falling in love with each other not knowing the identity of one another as enemy. Nevertheless, against their superior they've chosen love over their assignment. Whereas Bangkok Love Story is about an assassin develops feeling for his assigned target.

The plot in both of these series are similar. A virtuous hero chosen to lead the Mohist sect during the Warring Era China with a quest of abating war between the neighboring nations while soliciting unification for peace.
All the while, high ranks in the king's court felt threatened by the rise of our hero movements as acts of rebelling. Thus, they accused these heroes as spies with a malicious intent to bring down their nation. So they sent orders to post rewards for their head.
Beside the plots are alike, both of these stories also have many similar characters.
The only difference in these two series is that The Legend of Quin is not about time travel.
If you enjoy A Step into the Past (2018), I recommend The Legend of Qin (2015).