Both have winter settings with melo and calming feels. The main couple also met in highschool, then separated and reunited again.

They are historical k-dramas with fantasy elements, magic and evil spirits. 
Alchemy of Souls tell the complicated love story about a weak young master and a former assassin, who involved first in master-maid and teacher-pupil relationship. 
Lovers of the Red Sky is the love story about a blind astrologer and a painter.

This drama reminds me a lot of Weightlifting Fairy Kim Bok Joo. Of course both have different sports. But, both are youth sport dramas with the lead couple bickering vibes, friendship, dorm life, campus romance, and those sport trainings. If you loved Weightlifting Fairy, I recommend you to watch To Fly With You.

I watched Crush without having high hopes, I found a gem. Crush is a very good drama, then reminds me of an old drama which I always kept in my heart, that is That Winter, The Wind Blows. In Crush, ML is blind. In That Winter, The Wind Blows, FL is blind. Both dramas have outstanding cinematography, talented lead actors and amazing plots.

These two dramas are current airing dramas of 2021, which Xu Kai acted as male lead in both.
If you're watching one drama and waiting for new episodes, I hope you watch the another one too. Both are very good shows in their own genres.

Both are Chinese fantasy historical dramas starring Xu Kai as male leads.
Both have
- Beautiful pairing
- Amazing lead actors
- Demons, immortals.

Both are xianxia dramas aried in 2021. There are a lot of immortal characters, gods and different lifetimes of the leads.

Miss the Dragon's plot is somewhat similar to the mortal trial part of Eternal Love. Both are xianxia romances with immorals, reincarnations and life trials.

Main characters time-travelled to Joseon Dynasty from modern day. In MQ, he is a chef. In DJ, he is a doctor. They both used their own respective skills to help out people around them. They both were kinda entrepreneurs in Joseon.

1. MLs are immortals. In Nine-tailed, ML is a gumiho. In YWCFS, ML is an alien.
2. MLs are waiting for his first love (which turned out to be FLs) from Joseon Dynasty.

These two share a lot of similar concept. Both MLs are immortal with supernatural power. ML met first FL when FL was still a child, in Nine-tailed: ML saved FL, in Hwayugi, FL free ML from his prison.

Both are music dramas. Beethoven Virus was my first Korean drama, which display perfect Music Industry, love, friendship and struggles between 3 leads in an orchestra. DYLB also gives me similar vibes.