I really hope she's not in love with Ha Gi coz can't take another triangle ðŸ˜If you could spoil, put the spoiler…
(Note: There might be a few errors here and there since I read the webtoon in chinese using a translator) In the webtoon, Hagi protected Chan from school bullying and looked after him. Hagi was the most popular guy, the one everyone followed around. When they met Jeongyeon, they all became friends, but since she also had a dark past just like Chan, the two of them became really close. However, a girl ended up exposing Jeongyeon's past. To get revenge, knowing that this girl liked Hagi, Jeongyeon kissed him. Chan had always been completely alone until Hagi protected him, but he had started developing feelings for Jeongyeon. When he saw that happen, he just couldn't accept it. He ended up dropping out of school and becoming an idol. In the webtoon, Lee Chan kept the photo facedown, showing that while he hasn't forgotten about her, he still can't accept what happened and holds onto a kind of resentment. When Lee Chan realizes that Hagi likes Dareum and that Dareum is his own fan, he initially approaches her with not the best intentions, but he eventually ends up falling in love with her. After the storyline with Yoi Choon wraps up (she gets exiled after being exposed for mistreating staff), around chapter 60, Jeongyeon reappears and meets up with Hagi. Dareum sees Hagi with Jeongyeon and feels curious, or maybe jealous. However, Jeongyeon’s real goal was actually Lee Chan, and she notices that Lee Chan is also interested in Dareum. In the end, Jeongyeon leaves, and for Lee Chan, letting go of Jeongyeon is a part of his healing process, even though Hagi stays with Dareum.
I really hope she's not in love with Ha Gi coz can't take another triangle ðŸ˜If you could spoil, put the spoiler…
In the webtoon, she is attracted to Lee Chan because they both have a dark past, which makes them empathize with one another. The problem is that she ends up dating Hagi just to annoy a girl (who had previously exposed Jeongyeon's past) who liked him, which causes Lee Chan to become cynical, drop out of school and become an idol. (In the webtoon, Dareum found the photo at Lee Chan's house, not Hagi's, so something changed... maybe it will change in the drama as well). Later, she comes back, is still interested in Lee Chan, and goes on to bother Dareum. (There might be some inaccuracies since I read it quickly a while ago)
Yeonwoo is so pretty... She is going to play Han Jeong-yeon (or at least that's her name in the webtoon). To avoid giving spoilers, let's just say she's Hagi and Lee Chan's school friend. But she is a very important character in the second half of the webtoon.
In the webtoon, Hagi protected Chan from school bullying and looked after him. Hagi was the most popular guy, the one everyone followed around. When they met Jeongyeon, they all became friends, but since she also had a dark past just like Chan, the two of them became really close.
However, a girl ended up exposing Jeongyeon's past. To get revenge, knowing that this girl liked Hagi, Jeongyeon kissed him. Chan had always been completely alone until Hagi protected him, but he had started developing feelings for Jeongyeon. When he saw that happen, he just couldn't accept it. He ended up dropping out of school and becoming an idol. In the webtoon, Lee Chan kept the photo facedown, showing that while he hasn't forgotten about her, he still can't accept what happened and holds onto a kind of resentment.
When Lee Chan realizes that Hagi likes Dareum and that Dareum is his own fan, he initially approaches her with not the best intentions, but he eventually ends up falling in love with her.
After the storyline with Yoi Choon wraps up (she gets exiled after being exposed for mistreating staff), around chapter 60, Jeongyeon reappears and meets up with Hagi. Dareum sees Hagi with Jeongyeon and feels curious, or maybe jealous. However, Jeongyeon’s real goal was actually Lee Chan, and she notices that Lee Chan is also interested in Dareum. In the end, Jeongyeon leaves, and for Lee Chan, letting go of Jeongyeon is a part of his healing process, even though Hagi stays with Dareum.
Q&A (english) https://youtu.be/fggD8cj01hI