Title: 1/5

Your title seemed to give away your story's plot. So Seohyun's going to end up alone, right? Unless you twisted the story or changed the title(not sure). But the ending was obvious and you're just explaining how it became like this.

Foreword/Description: 9/10

Good. Just right.

Appearrance: 3/5

Yes, the poster's marvelous but, I thought Kai was the main lead at first-- since he's the only one staring at us. I do suggest you placing Chanyeol and Seohyun only in the poster. Otherwise, request for the co-starring characters to be smaller, this will not hinder the main characters.

Plot: 9/15

Originality: 8/15

I would say it's currently clique, but who knows what you may do for the next upcoming chaps? Why is this clique? The girl falls for the boy, but the boy doesn't/maybe like her. She is confused, but tells herself its a one-sided love. Then the third party comes in, which complicates the situation further when she is his childhood friend. And this also made it harder for her to know whether, or not, he likes her. And as expected, the childhood friend was really friendly and adored Seohyun, making(might) her hard to not hurt her(if Hyo likes Chanyeol too in the future) Then probably Seohyun becomes alone or Chanyeol likes her back(or falls for her), and maybe Hyoyeon has a another side-- to trash Seohyun and Chanyeol's friendship/relationship later on, etc.

Grammar: 12/20

As I've mentioned before for your one-shot fic, you often go on rambling your sentences out it one go (run-on sentences).

Examples:

"He has insanely deep voice that doesn't match his youthful face and ear-deafening loud laughter that is in the borderline between unexplainable oddness and goosebumps inducing creepiness."

"He is the first guy everyone would call out when they are asked to name a student from his year and that was how Park Chanyeol was elected to be President of student council when he was in his second year. "

"It all begun with unplanned lighthearted chatting that Chanyeol kindly initiated during their train ride home during her first few months in the student council."

Suggestions:

"He has an insanely deep voice which didn't match his youthful face, and an ear-deafening laughter that wavers between indescribable(unexplainable is not a word) oddness and goosebumps-- inducing creepiness."

"During the student council President elections, he was the first guy everyone had voted for from his year. And this, was also how Park Chanyeol became the President in his second year."

"It all begun during her first few months in the student council. 

It was an unplanned lighthearted chatting Chanyeol had initiated first during their train ride home."

Here are a few grammar mistakes(original/suggestion):

"... in the same time " (at the same time)

"... kept by herself" (kept to herself)

"...listen in the student council meeting" (listen to in the student council meeting)

"... she is greeted" (she was greeted)

"... that belongs to a" (belong to a)

"...as the treasurer of" (...in the treasurer of)

"... admit her interest" (admitted her interest)

"...her chest felt constricted" (her chest constrict)

This("to the bronze guy"), should be changed to "bronze-haired guy" instead of "bronze guy". Who knows, maybe Kai's a bronze statue.  

Wrong usage of (em)dashes:

"...and since he--the president of the student council--believed in her, she should too. "

Suggestion:

"...and since he, the president of the student council, believed in her, she trusted him."