Title

So far, there is little connection between the title and the story.  I assume that Hanneul will become Shinhwa’s light later on in the story.

The problem with naming a fanfic after a song is that there are so many other fanfics with the same title.

Description

Your description does a good job of drawing people in, especially when you include the question of “can they deal with Hanneul?”  It also portrays your OC as unique.

I don’t think that the scenes that you’ve included in the description are necessary.  One or two quotes would be fine, but not two entire scenes.

Foreword

Your author’s note is a good example of what a foreword should be.  You explain your reasons behind writing this fanfic as well as the reasons behind the title.

You do not need to include the names of the characters in your foreword, as you mention them in the character section when you write “Shinhwa & OC”.

Presentation

If you’re going to use colors in your foreword, I would stick to darker colors, such as a dark blue or dark purple.  Brighter colors hurt the eyes of the readers.  You do not need to italicize the author’s note either.

Spelling & Grammar

For the most part, spelling is good.

Your grammar is pretty good, but it still needs some work.  Since you’ve requested me to beta your fanfic, I will go over individual grammar mistakes with you through beta-ing.

Style

You use a lot of Korean words.  Some of them are necessary, such as “hyung” and “eonni”, while others are not.  Hanneul calls Hyesung “naui wangja” when she could easily say “my prince”.  She says “wae” when she could say “why”.  Dongwan says “arraso” when he could say “do you understand”.  Also, words like hyung and eonni do not need to be italicized.

Diction: Your vocabulary is pretty good, with the occasional out-of-place word.  If you use a thesaurus, then I would suggest putting the thesaurus away.

Syntax: Likewise, your sentence structure is pretty good. 

Imagery/Details: Sometimes, your imagery paints the wrong picture, such as when you describe Hanneul’s skin as “soft as a baby’s ”. 

Dialogue: Sometimes, the dialogue does not really match the personalities of your characters.  The Shinhwa members switch between sounding like trained assassins and sounding like teenagers.  When the Shinhwa members speak, try to make them sound more mature.  If you are unsure of how to make them sound more mature, listen to adults converse in the real world.  That should give you a taste of how adults speak, which should help you write the Shinhwa members’ dialogues. 

Flow

Your flow is good, not too fast or too slow.  Good job here!

Characterization

Hanneul: Hanneul’s character is difficult to characterize, mostly because of her mental instability.  She is childish and innocent, which you point out constantly through her actions and words.  I find it difficult for her character to grow unless her condition is cured, but that is okay. 

Eric: I see the most growth potential in Eric, who, at the moment, seems to have more flaws than good traits.  Eric absolutely hates Hanneul, and I can’t wait to see how you develop his character. 

Hyesung: Hyesung seems to play the stereotypical “oppa” role toward Hanneul.  The question is whether he will remain as Hanneul’s oppa or whether he will become something more.

Other Shinhwa members: The other four members of Shinhwa do not get as much coverage in your story as Eric and Hyesung.  It is up to you whether or not you choose to develop these four characters, but make sure not to become overwhelmed if you do.

A common theme I see throughout all of the Shinhwa members except Eric is that they act more like teenagers than men in their thirties.  They all immediately adapt to babysitting Hanneul, participating in her childish games at their first meeting.

Plot

Believability: While the plot itself is a bit of a stretch, the events that you include in it make it believable.  The interactions between Eric and the chairman, as well as when four Shinhwa members are sent to collect money make the plot believable.

Originality: There are original elements in your plot, but you’ve set up your plot so that there is potential for all of the Shinhwa members to fall for Hanneul in the future.

Consistency: Some scenes seem out of place, such as when you reference G-Dragon’s One of a Kind.  Just make sure to remember your original plot, and try not to stray from it too much.

Overall

I was really surprised that you chose Shinhwa to be your main characters because I really like them.  Thank you for requesting for a review, and I’m sorry that it took so long to complete.