Recommendations

diamond lover special cut is just a shorter version of diamond lover.

same kind of illness
secret idenaty
both mc's are very intelligent
same kind of subtle romance

- It shows the same thing about a girl who survive in the cruel world by herself.
- The power of woman who are smart person.
- Fun to watch.

both main leads were traumatized by the villain who killed both parents, and they grew up with the idea of revenge in mind

Both show how corrupt the government can be. Both have some crappy Prosecutors who only think of themselves. In Remember - War of the Son it deals with Alzheimer's and in Duel one of the characters has memory loss.

Both are crime dramas. Both are science-fiction. In Tunnel the main guy is looking for his kid. In Duel the main guy is searching for his missing daughter. However the two have completely different storylines. Tunnel has the time traveling aspect and Duel has the clone aspect.

> Another historical drama (WW2 era)
> Zanilia Zhao main lead
> Badass female lead
> Fights to win war (RAR) ~ whereas in PA she fights to get rid of slavery.

Same director using the same quirky style. However Memories of Matsuko has a much darker plot.

Empress Ki and Queen Insoo are both strong woman who are smart and cunning.

Akunin and Ikari have a sort of slow and sprawling dark narrative that feels quite similar. Both with an emphasis on human nature and paying close attention to the cinematography and music. If you like the one, you'll probably like the other.

Tsumabuki Satoshi is in both of these as well.

both have ghost romance(in "Bring it on,ghost" the lead fall in love with a ghost)
both have murder cases

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.

If you like kind a dark romance, something that's not only black & white - sometimes grey, when the male/female lead is only human and can made mistake - everyone made mistake and try to correct it, something psychological, steamy, smut and mature story. I think you can give KNH a try.
NB: there is too much of adult content, recommended for 17+ only.

Both start with the same plot of a humanoid robot to be the partner (taking care) of the main guy.

Both series are about vampire it also has
Action
Doctor
And the romance is good
But most importantly the main is totally hot