Recommendations

Both dramas are coming of age stories with everything that entails : high school drama, sweet first love, strict parents...
ML is also a transferred student, misunderstood because he doesn't "fit in"
But in Forever Love the romance goes further and we actually get to see the life of the characters after high school, university, work...

Both dramas are coming of age stories with everything that entails : high school drama, first love, strict parents...
Main difference is in Our Secret we get to see the life & the actual romance of the characters after high school, university, work...

The modern day spin-off/special has the same female leads and characters and is based on the events of Legend Of Yunze.

Both are murder mystery

Chip-in sets in a family house, with each family member as a suspect. Anata no ban desu sets in an apartment building where all the tenants are suspects.

The pace and tone of both Wish You and My Sweet Dear make for very similar viewing experiences. Both sets of mains show great love and passion towards their respective crafts and dreams, and their new, healthy relationships only add to their growth in their fields. And the way both series maturely and realistically handle the plot conflicts are very refreshing.

Similarities: Non-blood related sibling love, based on a 10 volume manga, happy ending.

Minato is a university student and has a fear of germs. She isn't interested in looking pretty. She lives with her stepbrother Toru, who is her stepbrother from her mother's remarriage. Meanwhile, Toru is handsome and a player with the ladies. He doesn't resist women who come on to him and he doesn't stop women from leaving him either. Minato is uncomfortable with Toru and his ways with women. They are the same age and attend the same university. They have an agreement, where Toru will not approach Minato within 2 meters when they are outside.
One day, due to her friend’s request, Minato puts on make-up and wears her friend’s high school uniform. While she is out walking in public, she happens to meet Toru. She unexpectedly lies to him about her identity and tells him that she is a high school student. Toru falls in love with her at first sight.

Both dramas are based on a high society, from what I noticed- Show Window: The Queen's House is less focused on academics as The Penthouse but both dramas are focused on stepping over others and cheating to become the richest and top in the society. In the Penthouse, everyone is obviously neighboring in the penthouse with people who will turn on you anytime for social gain, in the Show Window: The Queen's House- they neighbor in a "rich society only neighborhood." In both dramas, there will be a mystry murder that happens in the very end but is also the opening of the drama in the first episode as a flashback which keeps us guessing who the murdered person is and who the murderer is. In both, the wife is nice to the mistress, but that doesn't stop the mistress from being jealous anyways and doing anything to ruin the wife and steal her riches. In both, the husbands are trash and are only married to the wives to steal their riches and company. Very similar vibes. If you enjoyed The Penthouse, you'll definitely enjoy this.

In both dramas, the husband will be married to a woman and also have a mistress, he'll pretend to be devoted to both. The mistresses in both dramas will approach the wife and pretend to be friends with them. In both, there will be a mystery murder. The vibes and society are also very similar. If you liked high class, you will like Show Window: The Queen's House

In both dramas the female protagonist rarely withdraws from picking a fight about the injustices she encounters in the office. The guy is the timid one and often is viewed as someone or too angelic or as someone who is just too weird.

Both are about two people who may have feelings one for another. Both works at the same office. The guy work for the company for a longer period of time, while the girl is a newcomer with a omplicated pasts about her relationships and previous jobs. The guy is trying hard to suppress his anger towards his co-workers and is often walked over by them... The girl is the one who fight for justice.

Both shows revolves around three interns (two guys and a girl) who enter a company at the same time... and their young boss. The female intern starts raise her voice about the injustices in the company and drags into the fights her co-workers. She and her boss starts to develop feelings one for another.

A number of topics, is very similar to "Dangerous Drugs of Sex".
Sexual assault, rape, grooming, the victim learning to accept the assault and romanticization of former sexual abused victims.

Both have a starring female character. In 'Find me if you can', the 3 male characters like the main character, while in 'Boyfri3nds', the 3 male characters are her 3 boyfriends. While 'Find me if you can' is mostly focused on a darker topic- stalking, it also has a surrounding romance and comedic plot, while 'Boyfri3nds' is mostly focused on romance and comedy.

(SPOILER: There is a slightly darker plot-twist).

Both are mystery-thriller dramas and they both have an 'investigation' to find the 'culprit' behind the act. 'Rumor' is somewhat darker than 'Find me if you can' (which has lighter moments). Both dramas are based on real-life topics: 'Find me if you can' is based on stalking and also showcases bullying. kidnapping, manipulation. While, 'Rumors' is based on rumors (obv) and their effect on people, being a victim of workplace bullying and judgement.

Unproblematic and mature love story
Everyday life and cute romance
Follow the lead through years
Incredible chemistry between the leads
The give the same "good/romantic" vibes