Recommendations

If there's ever a drama that's accurately similar to Soundtrack it's this one.
In time with you takes a proper line as it's a full drama with a magnificent focus on unrequited love and how it blossoms.

Both have similar vibes about a virus infection and changing peoples mind.
Dark hole is produced on a large scale and has action sequences.
Crows blood is more of drama however has some gory blood scenes. Is happens in the school setup. Though its not a great series, just can be seen if someone has inclination for this genre.

If someone likes this kind of theme, they can try crows bblood.

Addicted wasn’t given the mature rating it deserves. KinnPorsche gives you that with great production value.

Both are Thai BL romance dramas loosely focused on food and desert-preparing.
Atleast one of the male protagonists have a deep childhood-trauma that impaired his life and is connected with his motherly figure. One of the protagonists is painfully shy.
The gay guys have a female friend that can be and wants to be of help to them.

Both are quirky, fun, and unique short dramas in a school setting. Both have fourth-wall-breaking elements (the actors and characters have the same names, and CYH lets the viewer choose the ending), and light fantasy elements (the "ghost" of a coma patient as a character vs. the "inner personality" of the FL as a character).

Fluffy, cute, and quirky dramas in a school setting. The FL is extraverted and somewhat awkward, ML is somewhat aloof/distant. FL chases the ML first.

Fluffy, sweet romances in a school setting.
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The story itself is not really similar. I'd say they're nothing alike, but part of the cast and production team are the same. So if you've enjoyed the quality Why R U? gave you even amid COVID-19, they'll be doing a lot better now with Middleman's Love.

Frenemies to romance. Both are school set and light in tone youth dramas.
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Childhood friends to romance within a circle of friends/schoolmates. School setting. Both are sweet and mostly light youth dramas.

School setting, sweet light romance.
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Three childhood friends that are separated when young, but all end up colliding/meeting again as adults. A mystery surrounds the reason for separation. Series has love, but its focus is also on friends and family.....with the question of is it possible to start again? Both has a serious undertone, but on the top it is all cute and fluffy with positive ending.

Both dramas reunite two actors, Huang Sheng Chi and Ma Xin Yu. However, Mountains and Oceans is quite darker (especially in the last episodes) and the two actors have very different parts in the two dramas :
-in Believe in Love, Huang Sheng Chi is the male lead and Ma Xin Yu is his sister, a spoiled noble lady
-in Mountains and Oceans, He’s the second male lead with a tragic fate while Ma Xin Yu has a much more important part, the second female lead and villain of the story who gets consumed by hatred and envy for the female lead and that you will definitely hate to the bone (but her performance is stellar !)

They are both office romances and have a light-hearted feeling/vibe to the shows. Two soft hearted people falling in love in both series.

Both try to explore the relationship between the male escort and the female sponsor, always keeping the drama to keep the audience invested.