Title:
While the title relates to the story, obviously, it's not really anything unique to me. If I saw it on the recently updated stories, I probably wouldn't click it because all I'd be thinking is: "Oh, it's another one of those types of stories, next." Since I tend to judge titles first when looking at books. If I see an interesting title, I'll pick it up, look at the cover and if I like that - I'll read the "description" then decide if I want to read it or not. For people like me, title is quite important since it is what judges if we look further into it or not. So overall, it's not the most unique title in the world but really, it's not the worst I've seen either. All that matters is that it connects to what you're writing and it does.

Description/Foreword:
The description is pretty self explanatory, really. It pretty much brings up the concept of a "soulmate timer", showing what type of soulmate AU this will be mostly. The foreword is nice too because of the quote, I think that quote truthfully fits the story rather well so it's perfect. I think the description and foreword really are fine as they are. I don't see anything wrong with them. 

*Plot:
While I do like soulmate AU's and so on, they can be really cliché and they are very overused so it's hard to find something original with them. It's always the same few things and, in truth, I've read stories with these so-called "soulmate timers" and how they hit zero after the soulmates have either met or one has died so I can't say the idea is really original - mainly generic. The one thing I found interesting though is that is literally is a "timer" that you have to "implant" per se. Most of the time, (one's I've read at least) make it so that when the person turns 18, they get a timer similar to a tattoo on their wrist so this was different.

*Writing Style/Flow:
I did notice some awkward things, sentence wise and such, here and there.

Example 01 in CH1: "Just like their everyday life, there were only Ahyeon and her sister[...]" 
What's wrong here is "there were only", it would be "there was only".

Example 02: "loud mouth with a duct tape." 
What's wrong here is the "a" before duct tape. It would be "loud mouth with duct tape." Duct tape is duct tape regardless of how many are used. "There's two rolls of duct tape." or "There's only enough for one strip of duct tape." It's just one of those words.

Example 03: "Maybe it was because the air cond" 
In writing, you shouldn't shorten words like that. Using the term "AC" would have been acceptable since most people, even in speech, do say AC but saying "air cond" is kind of silly. You would write it out as "conditioner" despite the fact that, yes, everyone knows what you mean - it's just more about the so-called 'properness' of it. You wouldn't see "Air cond" in a book.

Example 04: "Besides, you've also implanted the timer sometime ago, don't you?" 
While this sentence is almost fully correct, it's the "don't you" is what kind of throws it off since don't means "do not". So literally, this says "do not you?" Which doesn't make much sense. I would replace "don't you" with something like "right?" because he's asking for clarification on the matter of subject.

Example 05: "You guys saw Bobby yet?" 
It would be: "You guys see Bobby yet?" since 'saw' is more of a past tense thing. "I saw him yesterday" or "I saw them at the mall a little while ago." it indicates past tense.

These are the ones I managed to see and truthfully, they're very minor so it's not that big of a deal but since you wanted focus on this section [I think], I decided to point out what I saw. There wasn't much to be honest.

As for the flow, I'm unsure truthfully. One side says sure, it's fine, while the other thinks it's a bit scattered. Maybe it's in between which isn't a bad thing, unless it gets confusing then it gets bad, but it's hard to really tell since the story is only three chapters. Though, really, I wasn't expecting her to get the "timer" so fast so maybe that's why I had second thoughts.

Characterization:
Looking at the two male lead roles of the story, they're both very generic and cliché. Of course, you have the "smart" and almost "perfect" one who is the best friend and then the complete opposite which would be the so-called "bad boy".

This is overdone big time and I've seen a bazillion fanfictions with male roles (or even female roles) with these personalities. While there does seem to be more to Hanbin then we know right now, he still comes off as that generic kind of hardass. I have a feeling this will change in later chapters so I'm not that concerned about Hanbin.

As for Donghyuk, I'm not really sure. I think the way he's described in the beginning kind of made me tilt my head since in reality, no one is perfect even if we say they are. People live to be quite unperfect and even idols aren't perfect, especially since we don't see what happens in the personal life. While there are people who are smart and participate in activities and stuff such as student council, I feel like this concept is quite overused in terms of fanfictions since almost everyone uses it. While it does kind of fit this kind of story, it just doesn't seem unique.

And for the final character, the female. I don't know, she doesn't really stand out. If I put her up against, I don't know, other OCs, she might not really stand out much since her personality isn't unique. She's just kind of like every other OC out there even though she isn't at the same time.

Personal Enjoyment:
In truth, it's not something I'd read since I don't like OC fanfics very much but it's a start to something, definitely. I know it's not very "popular" right now and that can be discouraging but I hope you continue writing it because I think the story, like every story, has potential to become something good. It's just hard for stories to be noticed when so many are uploaded and updated a day. Just keep writing and I think you'll get somewhere good. (I hope I made sense here it's almost 3:40am)