Chapter 3: Yoohyun must be a realist to not believe in the supernatural. Since horror is more of Songjin's thing, it doesn't seem that she'd be interested in anything romance-related. Her friend does sound desperate about wanting a boyfriend. There's got to be a reason behind that. Something must've influenced her thinking.

Typos:

I mean, it's impossible that a thing like this...exist.
Correction: exists
* "Thing" seems to be the subject that is referred to by this verb.

You keep complaining that you don't have a boyfriend and yet, you can't believe how a match-making device that can help your own love life exists.
Correction: You keep complaining that you don't have a boyfriend, and yet, you can't believe that a matchmaking device can help your own love life exist.
* Exist is not the main verb here, so no conjugation is needed since it is not directed towards any subject.

Yoohyun looked at the device again, and continued to stare at it.
* The comma is not needed since there's no subject before the verb in that phrase. This also disrupts the smooth flow of the sentence.

Chapter 2: There's definitely something not right about Hwari. She gives off the impression of being a hypocrite. Someone like that can't be trusted. All stories have a villain/antagonist or a conflicting force that challenges the protagonist.

A little editing is needed here. The prepositional phrase should be "in the hallway" since that's an indoor area. In the sentence where you have two verbs next to each other (flirtingtalking), it looks awkward. Only one verb must be used. "Flirting" seems to be the obvious choice in this case since Hwari is turning on the charm and sweet talking to Myungsoo.

Chapter 1: It seems to be a machine that randomly matches up people together according to their ideals. Since there are a plentiful amount of guys in the world, the matchmaking should be able to come up with more than one possibility. However, this machine decidedly narrows it down to one person that fits her ideal type. It's unreal that it has the ability to see into a person't true nature.

The teasers are bound to build up our interest in the story.

No problem! I don't mind sharing my thoughts. You'll be seeing me do this for every updated chapter. It would be interesting to see what others think while they're reading this fic. I'm already reading this, so I am sticking around for more since this story grabbed my interest when I first came across it.

This looks like an intersting plot. The thing with machines is that they can't really measure love. It's like a fortune-telling machine that's built to catch people's attention by making predictions, but they actually don't come true. That's the reality of it, but anything can happen in the fictional world. There's not much that I can say until the story gets rolling.