Lovely Runner and Our Beloved Summer's FLs are having depression, similar with FL in The First Frost. And MLs are the blinding light that shine through their dark life.
At one point FL in Lovely Runner break up with ML for his safety just like when FL in The First Frost flee to Hongkong.
At one point (while in university iirc) FL in Our Beloved Summer break up with ML because she feels like she's not good enough for ML and she's having so many things in her mind just like when FL in The First Frost go to another city (Yihe?) also while in university.
For Because This is My First Life maybe because both dramas have roommate to lovers troupe? I can't really remember the detail since it's been so long.
I think there will always be similarity if someone gives recommendation(s). They usually write some notes under the recommendation(s).