Recommendations

Both of these mystery-thriller dramas center around a female lead, and those around her, who doesn't believe that her twin's deathly fall was a suicide.

Both are set in the Republican era and have a similar premise with characters that have a ambivalent relationship dynamic.

First Lady is the sequel to First Nanny, so if you want to check out the story that came before - watch First Nanny.

Here are some similarities between YAMG and Hi Venus:

1. Healthy Relationship
2. Green flag characters
3. Heartwarming love story
4. Typical comfort dramas
5. No breakup after the main lead get together

Both have fantasy element. COALG focus more on mystery and conspiracy while Island go deeper into the fantasy story. But both have subtle romance story. If you like fantasy drama with a slight romance, both dramas are definitely recommended

Love in Sky shares thematic similarities with Nineteen to Twenty despite their different premises, as both shows revolve around the experiences and relationships of young adults.

Same Main Couple.
But the Storyline is better and less cringe(er) (in my opinion that is )
Where First is a play boy and JaFirst are dating. You get to see possessive Ja too

"If I am the right person for you then from now on, you can't say no to me."

From friends to lovers. How will this relationship go, when one is a good guy but the other one is a bad boy. Is it possible to turn a bad boy into a lover?

(Source: BL Update 2020 Instagram)

~~ Adapted from the novel "Don't Say No When Hearts Are Close" by Mame.

Real High School Romance and Nineteen to Twenty share thematic similarities centered around the experiences of young individuals in pivotal life stages. Both shows capture the essence of youth, growth, and the transformative journey into adulthood.

I believe the characters share similar vibes. The main leads, who are passive in nature, resemble each other greatly – initially hesitant to embrace change, but eventually discovering an unexpected partner for their future, someone who proves to be both understanding and loving, as well as profoundly supportive.

This drama has a completely different plotline from I DON'T LOVE YOU YET. But, it gives the same vibes as the latter... Probably because the director is the same.
If you are interested in the same slow paced buildup dramas, you might find it great.
Though, Kimi wa petto does have some quirky/ even mature elements but the character development goes on well and you feel satisfied completing it.
I am not recommending the old Kimi wa Petto drama because it is not related to this drama... But if you like Kimi wa Petto (2017) , do try out the old version as well...

The leads are comparable to the leads in the devil judge. Despite their different world view, they love and care for each other. However unlike in the devil judge, The leads have a deep trust and understanding of each other.

Both dramas are typical Noona romance-style
The leads are childhood friends and quite close.
In both dramas, the ML is the first one to realize she has feelings for the FL and starts pursuing her.
FLs in both have had unsuccessful relationships and find solace in the MLs.
very romantic and cute drams

childhood lovers who are not related by blood but grew up together.
Noona romance.
Both are about a career woman and a bubbly, playful ML who is head over heels for the FL.
Very sweet and romantic, minimum angst.

Both FLs are strong in character and have to pretend to be well-behaved in a big family where their real mother is a concubine.

Feng Shao Feng is the ML in this drama. He acted the role of GTY brilliantly ie. an uncut diamond.

Both shows feature an office romance, in which the main couple have a Boss/employee relationship. In both shows the boss is the son of the company owner.

The main difference is that Poongduck 304 heavily features the main leads living together as part of their conflict, as well as being a Korean BL compared to Step by Step which is Thai.