There isn't really much of a description, but the warnings you have are a good indication of what the story involves. But still, a little brief synopsis would be nice.

I thought your foreword was very effective. You outline each character and their relationships within a small passage which was very well done. And you did it without giving too much away - you did well in this aspect.

At first, I found your story quite hard to get into. Series 1 focuses on each character individually, and I felt it made things go a little too slow at the start. I completely understand why you did it, and it was beneficial for readers during Series 2. But I think you could've incorporated the details of series 1 into series 2, but at the same time, it's also fine the way it is. I wouldn't bother changing it. 

When it came to series 2, things really began to pick up and I found myself enjoying the story much more.

Your plot wasn't exactly original, but I thought you put your own spin on it well. You also kept a nice flow. I also really liked how it wasn't just one plot line - you incorporated a few, and you did it in a way that didn't feel messy or overwhelming. 

I also liked how you tackled issues that were relatable to the readers, and majority of it was pretty realistic. 

The only criticisms that I have are:

If Hyunju has an eating disorder, and Jackson is aware of it, I don't think he'd get her released. Sure, Hyunju may have convinced him otherwise, but if she's in hospital, she's in there for a reason. She wouldn't be admitted if she was okay. As a friend, I think Jackson would want her to fully recover first. 

Also, I felt like while the ending of the story did tie up the loose ends, I kind of wanted things to be more in-depth. Like, who is the girl Iseul is with? Where is Jackson working? What exactly happened to Mark? I know these things are implied, but I felt I wanted to know more about what happened to them.

Generally, I quite liked your characters. I felt like you made them genuine and likeable which was nice. And they were pretty three dimensional. 
You also had a good mix and contrast within your characters.

Yugyeom was such a cutie, and Hyunju was such a poor soul. I liked how you built a feeling of inevitability in the lead up to her death, and just generally her downward spiral was well done.

I wish we could've seen more of Mark though. I felt like he was terribly misunderstood, and I felt like it would've been really interesting to see things from his view, and his feelings about Hyunju's death. 

I also wish we'd seen more of Iseul's confusion concerning her uality, and just generally the degeneration of her relationship with Jackson.

You kept a nice consistent voice throughout the story. While your style could be considered basic, I don't think it took away from the story at all. 

I thought your grammar was okay, especially when English isn't your first language, but I noticed a couple of recurring mistakes, such as:

You often said something along the lines of "They sat on the table.", but it should be "They sat at the table."

I thought your layout was pretty nice - though your foreword and description could be considered a little messy.

I also thought your poster was cool, especially the fact that it's animated.