1. Lee Won Geun is the main lead.
2. Both have sweet, youthful content.
3. Both have love-triangle

1. Lee Jun Ki is the male lead of these two dramas so if you're a fan of him, you should check this out.
2. both are historical dramas and the characters of Jun Ki both have complicated background. In Iljimae, his dad is called the traitor of the country while in moon lovers, his mom hated him a lot. And family is the main key thing to his decision. Revenge.

If you are finding some Kdramas with that second male lead syndrome then both of these dramas are made for you. Those two 2nd lead are caring, always there when she needs, a sweet-hearted guy but female leads didn't choose them in the end... =(

1. Both of these dramas have the sweet, light-hearted content and based on lives of college/ high school students. In "To the beautiful you", Kang Tae Joon (Minho Shinee) is a high jump competitor while Kim Bokjoo (Lee Sungkyung) in "Weightlifting Fairy" and her partner, Jonghyun (Nam Joohyuk) are majored in weightlifting and swimming in respectively.
2. The main male leads are both known as the "hot boy" at schools with handsome look and amazing talent in their own majors. Somehow, they also struggle with their sporting career. If Kang Tae Joon got an accident that could potentially ruin his future career as an athlete, then Jonghyun's trauma is the only thing that gets in the way of his success.
3. Kang Tae Joon and Jonghyun each used to be really cold-hearted until the female leads come to light up their worlds.
4. There's always a second female lead who had a relationship with the main male lead- "To the beautiful you", Seol Hana (Jiwon) is his childhood friend and loves him for a really long time while Siho (Soojin) is his ex-girlfriend who still has some feelings for him. Both always try to annoy the female leads.