Journey To the Core of Terra

Title (5/10)

I don’t think I’ve seen a story with your title before on AFF so this is definitely unique! I understand its link to the story and relevance. Unfortunately, if I was to browse through the stories it would not have caught my attention. It bares too much resemblance to Journey to the Center of the Earth from structure to meaning and sadly, that’s where a lot of points have been taken away – not interesting for me. Seeing as how extensive your use of vocabulary is, I was actually slightly disappointed at how boring this title was. 
Foreword (10/10)
From the foreword, you already produce an aura of mystery for this unknown land! It grabs the reader’s attention and makes them wonder what Yunho and Jessica will need to go through. Already here, you’ve introduced the themes of romance, possible threat and adventure - so great job! 
One small thing I would suggest is your last sentence: Can Jessica protect herself, and her heart? To add a little bit more ooph to that I’d probably write: Can Jessica protect herself, but more importantly, her heart? 
The placement of the character chart isn’t bad. I have a small issue with how some of the photos are squished (ex. Yoona) and it doesn’t look as nice. The creation of a map for your world is quite creative! 
All in all, your foreword is captivating and if I were to stumble upon your story randomly, it would draw me in!
Plot (26/35)
First things first, I think that the world of Hwa you’ve created is extremely vivid due to all the description you’ve put in! I want to give you a round of applause for making it seem so magical and exciting. I would not say your plot is original, as I have read stories along the lines of yours… however, yours is the first fanfic with this plotline so I’ll give you some points for that. There were no gaping plot holes and as I’ve mentioned (throughout) you’ve got a very elegant writing style with an expansive use of vocabulary that really wows your audience. Also, let me say that it was quite an interesting turn the story took near the end!
At the same time, where you excel is where I believe is a bit of your downfall. You spend a lot of time explaining things and giving details where I will admit there were times I decided to skip over. As an adventure story, I really wish the flow of the story was faster. I kept waiting for something drastic to happen (it was mentioned in the foreword about the dangers Jessica was about to face) but for a good portion of the story, all the dangers Jessica faced were quickly resolved with the presence and powers of the people around her. It made for a very predictable storyline where I’m thinking, “Oh crap. She’s facing a Daemon/a person that’s dangerous, but someone is going to protect her.” And for that, is where I have taken points off.

Characters (15/20)
You have a lot of characters so I’m going to be focusing on three: Yunho, Jessica, and Taeyeon. 
To be frank, I was (still am) a little shocked at how hard and fast Jessica fell for Yunho. Perhaps you left that five-year gap as up for our imagination but it was too random for me once you jumped back into the story about everything she was doing for him. I couldn’t identify with the emotions Jessica felt. However, the end when Jessica grows from being impulsive and in a way, childish to being understanding and accepting was charming. 
Taeyeon to me was a very mousy girl. The way she is in Jessica’s eye is squeamish but she also has a giant heart. She is a very nice contrast to Jessica who is more fiery. I liked Taeyeon’s character a lot and what she contributed to Jessica’s development. 
Yunho seemed to have the least character development of all. Perhaps it was the fact that you never told the story in his POV and more of what Jessica thought of him and what other people observed… I’m not sure. But he is still the stoic but intelligent Commander from beginning to end. He did change from being caught up in being in love with one person to learning to move on so I will give some points for that. 
Grammar (19/20)
Overall, your use of vocabulary and grammar is good! The images you paint with your words are impressive, so job well done! I do enjoy stories that are well written and yours definitely falls into that category! 
But, to complete my job, I’m going to point out a couple of small things: 
One of the first things that popped out at me while I was reading, however, is your use of commas. While they are for bridging together ideas, there are times where you use them excessively and make a sentence too long. There are also times when you’ve inserted them where they’re not needed. It’s sometimes taxing on the eyes to view such a long sentence. 
Ex. As Jessica shuffled over the crisp grass, and dense vegetation of the artificial woods, she saw a darkness more black than the one that surrounded her. 
Two things I would point out here: 1) there is no need for a comma between grass and and 2) I would not use more black as that’s inaccurate – stick to blacker. 
Rewritten: As Jessica shuffled over the crisp grass and dense vegetation of the artificial woods, she saw a darkness blacker than the one that surrounded her. 
This is honestly so minor, but I thought I’d point it out for your future benefit! 
Two: don’t feel afraid to use dashes or semicolons! Replace your commas with them and they’ll have a bigger impact! 
Ex. Worse, there were Daemons dwelling in the Glen, and she was in no means equipped with survival skills to fight them. Only Militants roamed the Glen to sharpen their dexterity and manipulation of their Chi. 
Rewritten: Worse: there were Daemons dwelling in the Glen – she in no means equipped with survival skills to fight them – and only Militants roamed… \
Three: While I have applauded you for your large vocabulary and diverse use of words, there are times I feel that it is a little excessive. True, it’s boring to use words like “said” or “feeling” excessively, but there were times when you use such large words in succession where it takes away from the simplicity of a well-written story. While I was able to recognize the words you’ve used, if other readers are in need to constantly look on Google of what a certain word means, it’s not that fun. So my suggestion would be for you to pick and choose when you may want to replace a word. Never underestimate the power of simplicity! 
Overall Enjoyment (3/5)
Despite everything I’ve said, I did enjoy reading your story! Your writing style is very elegant and expressive – I could see this being made into a movie. This score seems low purely because I wish I was in even more. There was so much potential but I felt like that story dragged. I kept craving for more. I do see you’re planning to make this into a series with an expansive exploration in the world you’ve created so I’m excited to see what else you’ve got in store! I do hope you have found this review helpful; you’re a great writer so keep at it!