Key to Her Soul by KatyMikayla

-Your foreword and description weren't bad. The quote is fine; perhaps a bit straightforward but relevant.

-The prologue seemed fairly well written and left me a bit curious. It's a little awkward how you bring up things that aren't really connected to the plot at all- like this cave thing Eunji goes into. And what is this revenge Kyuhyun is thinking about? You mention them, but don't really expand on them later, so they become these awkward extraneous things that might make the reader confused.

-On the other hand, your foreword is really wordy.

- I don't like your "How to Read" section because a) it was more of a "key" and b) it didn't tell me how to read it at all. Also, most of this, you don't actually need to tell your readers. They aren't stupid; they can figure this out on their own.

- I see you have a lot of other reviews, so I'm not going to focus a lot on elements like grammar, since I personally don't like nitpicking and I figure most shops do that pretty well so you have enough examples.

Plot: ☆☆☆ (3.5/5)

Okay, you can create a story that has a beginning, middle, and end- which is good. The basic plot is pretty clear, but there's a lot of little things that built up to make your plot pretty weak. For example, what I mentioned in about your foreword. My advice would be to cut all this unnecessary stuff and focus on making sure your plot is sound. The problem with having read so much romance (both fanfiction and literary) is that I'm a harsher judge to the plot. Why are Eunji and Donghae soul mates? You write the story after they meet and are in a relationship and all that jazz, so the reader doesn't get a lot of background on it. Their bond as soul mates shows a lot in the instant connection they have, but even within the realm of fantasy, I don't think "soul mates" is a compelling enough reason alone for their... I would say attraction, but Eunji is still a fox in the moments I'm thinking of. Try adding more detail into their bond; even as soul mates, their relationship should grow and change.
I really would have liked more clarification and detailing on other parts- How can Donghwa tell that it's Eunji if Donghae can't (and they're soul mates)? What happened in the cave? What happened in all these thousands of years in-between? What are Luhan and Sehun's backgrounds? And Donghae's motive for not investigating Eunji doesn't make sense to me- I'd understand if he were a bureaucrat or something similar, but as a scholar, shouldn't he be curious? And from my point of view, a lot of historical scholars were crazy anyway; he wouldn't have seemed much different.
I give you points for the fantasy elements, but the ending fell a bit flat for me. I was expecting so much more after three chapters of buildup, but in the end, the character's emotions and change are barely mentioned and all you do is describe this process of soul key and lock. The concept was pretty out of the blue- I feel like it was rarely, if not never, mentioned at all before, even though it's central to the title. Having mentions of this process would have made the ending a bit more cohesive. 

Overall, your plot is actually pretty good, but it can improve a lot. Create meaningful background (don't just add things for the heck of it) and either go into more detail for either romance or fantasy and your plot will be a lot more solid.

Characterization: ☆☆(2.5/5)

This sounds really awkward but literally every chapter there were times where I had to stop and ask myself, why am I getting some e vibes? 
So my main problems with this is that Luhan is 8, acts like he's 5, and then apparently is 2000+ years old (but still acts like he's 5.) The thing is, I get it, Luhan is pure. But there's a difference between innocence because of age and true innocence (and he doesn't come off as innocently naive- he just comes off like a perpetual five year old.) Also, I don't know if you've been around children a lot, but this isn't really how they act either. So I pictured him as a 5 year old because I get my head around anybody older than that acting in that manner, which made the implications of high rated events between him and Sehun pretty off-putting. If he's been around for thousands of years, Luhan will change. He can still be innocent, but he won't be the same blissfully ignorant child anymore.
On the other hand, I found Kyuhyun really manipulative at first (because of the Prologue) but after reading the fic, I wasn't sure what to think. I feel like there are times when you try to paint him as a "nice" character. So when he does things like threaten Luhan, it becomes really OOC (out of character)...
You characterize Donghae very childishly, and even when he's older, he still demands things like a child (“You’re mine and no one else’s.”) He seems very much the same character from when we see him as a child to when he's grown up. In addition, even though he denies , it definitely comes off that way, especially because he sees Eunji only as a fox. It would have been more realistic for him to have a bond more like the type people have with their pets, but stronger, and then reveal she's a woman. But his quick love for her once he finds out she's a demon wasn't very believable.
Eunji wasn't a character I particularly liked either. She has the power to destroy building after building (and so does Kyuhyun for that matter) but she seems so weak. The parts where she loses faith in Donghae don't seem to fit her character (at the same time, I don't like  In the end, all I have of her character is how much she cares for Donghae, which made her feel very one-dimensional. She exists without Donghae, but without him, I barely know who she is.

I don't mind you writing characters that are different than their stage personas but they could be a lot less one-dinmensional if characterized them more, either by adding small details and reactions in existing scenes to build a better picture of the characters or focusing more on it throughout.

Flow: ☆☆☆(3/5)

The biggest thing was that your dialogue is really awkward at times. It seems like you make an effort to make the speech fit a certain time period, with wording like  “And people scorned at us for sharing a cup amongst ourselves.” But then there are parts like “You are such a troll, Daddy” that are just too colloquial. And then you have Sehun saying “You’re so not going to be able to walk after I’m done with you," which is a) when my radar said E because I still couldn't figure out what age Luhan was and b) felt really awkward because you have a lot of people speaking formally and with. So if you want this to be modern speech, that could work. But if you're going to try and have time-specific language, make sure nothing is OOC.

Then you have parts that drift off the main plot. I understand trying to characterize minor characters, but parts like Zhou Mi having a crush on Henry are unnecessary. If you were to have one or two friends of Donghae be minor characters and have more than one or two scenes with them, so they could become characters we remember, this would be fine. But it feels like you're adding this scene simply to play to another ship. And like I mentioned before, the random parts about the cave and revenge were largely ignored by the main plot.

When you write longer fic, try to be more aware of what you plan to happen, or go back and change things if you're writing spur of the moment. It seems like sometimes you have an idea and you want to go somewhere with it, but then you don't mention it again later on.

For your first story, this was actually very good! Try observing how people talk in real life and emulate that in your writing. Flow is something you get better at the more you write so just keep writing. 

Originality: ☆☆☆(3.5/5)

As someone who frankly avoids fantasy, I'd say just about any fantasy plot seems original to me. I took of points for the romance aspect, because soul mates are a bit overused and you didn't expand on it enough for it to be something different.

Grammar/Spelling: ☆☆☆☆(4/5)

Spelling was fine, and there were a few grammatical mistakes overall- some tense problems, a couple clauses where the verbs weren't parallel (I think), etc., but nothing too big. The sentence structures were pretty simple, but that's okay, especially if English isn't your first language.

Overall: ☆☆☆(3/5)

Apparently I'm supposed to use this for how much I like the fic, but I usually just end up repeating the other ones. I like my fantasy with a lot of universe building, but we only get hints of that here. I think the romance is a bit overplayed, but overall, your story isn't bad. With some improvement, I think you have the potential to become a really good writer!

First of all, I hope this review was helpful! Please keep in mind, I value plot and characterization a lot so I grade them more harshly and weigh them more in my overall score. Let me know if you have any questions.

Your reviewer,
Lee