Title: The title is good. And I hate to do this but, "The mask of the full moon" doesn't really roll off the tongue. In my opinion using 'the' twice hinders the stories potential to draw readers in. Maybe try "The mask of a full moon". Seeing as you already have a poster made for it, I will suggest that you avoid that in the future.

Description: I also have suggestions on how to edit this as well as your forward.

Description: 

Yours: "Some say it's the work of a man. Others, a beast." 

The second part is an incomplete sentence. Others what a beast? 

My suggestion: "Some say it's the work of a man. Others say it's a beast.

Yours: "I will honor the man you once were. Not the monster you've become."

This ones wording is good. But, you can combine it into one sentence. essentially it's one complete thought as a whole. It doesn't need to be divided.

My suggestion: "I will honor the man you once were, not the beast you've become."

Yours: "You're scared of me because you can't control me. That's because you can't and you don't."

This one is the main one I had an issue with. You basically just repleated yourself. You already stated that he can't control you. It took me a little bit of playing around with the wording to get it to sound right. I don't know if this is going to have a romance aspect to it or not, so forgive me.

My suggestion:"You're scared of me because you can't control me. That's because you can, but you won't."

or

"You're scared of me because you want to control me, but can't."

Forward:

My suggested edits will be in red.

In January of 1871 an assortment of unsolved murder cases aroused arose in Seoul. Victims disappeared with out a trace, and each time, there would only be a paw print of an unknown creature. Each time. the only clue left behind was the paw print of an unknown creature. In On rare occasions there would be traces of blood. Whether it be the beast's or the people belonged to the beast or it's prey, no one ever knew. Inspector Kin Jongin and the police work day and night to track down the mysterious instigator. With the help of the local police, Inspector Kim Jongin works day and night to track down the mysterious killer. There is only one clue that seems to fit in; he strikes on the night of a full moon. It's seems the piece of the puzzle he has is that the perpetrator only strikes on the night of a full moon. While Jongin does all he could can to find a solution, he suddenly discovers finds himself being drawn to Cha Ae Sook, a normal girl he unintentially meets runs into repeatedly. No matter how hard he  tries they try, they he just can't seem to get away from her each other, and Cha Ae Sook finds herself dealing with the same problem.

However, every night during the manifestation of disappearances when another person's life is claimed by the beast, is it a coincidence that Inspector Jong in is nowhere to be found?

Can Inspector Jongin put a stop to the beast once and for all, or will he be the scapegoat victim?

Will Jongin be distracted by from his duties once he meets Cha Ae Sook, the girl that who turns his life upside down

Plot/Originality: The plot seems unique. Not many people choose to write about murder, let alone a murder mystery. If they do it's usually poorly executed.

Language: Your story is in dire need of an editor. One that can reword your work in a way that flows in a smooth manner.

Character: The story is not complete yet so I cannot be the judged of the characters development just yet.

Flow: There are a lot of inconsistencies. For example, the year is 1871, did you research what a camera looked like in 1871? It is quiet large and a lot of work to move. On top of that the effort it would take to just get a few pictures is not something that happened back then. I suggest you research a little more

Enjoyment: To be determined upon story completion.