[Suzerain of Sheol]

Okay, I read it.

I'll say one thing right away in your favor: Your spelling and grammar are competent. Reading this wasn't an exercise in wanting to gouge my eyes out at the number of errors. Good job. Seriously, I know it sounds ridiculous, but it's honestly surprising to see in creative writing I've found online.

Other than that, part of me wants to say that Mark is a really shallow character, only... he reminds me a lot of someone I knew in high school, so, maybe he's actually realistic.

As for the characters, I'll admit I'm not a very good judge of this sort of situation. They both seem really superficial and impulsive, but I have the feeling that's kind of the point. So, take that for what you will.

There are problems with the story, but rather than go through and make an extensive list of them, I can tell you instead what will fix most of them:

Show, don't tell.

It's the writer's mantra, the simplest truth of good writing. If you look at your story here, it's written in the fashion "They did this, then they did this, she felt this way," and so on. What this does is prevent the reader from really getting into the story.

So, what you need to work on is immersing the reader in the story, and you do this by showing them what's going on, rather than just listing it off. Put them inside of Natalie's head and let them feel what she feels. Give sensory details, like what she sees or smells, rather than just describing how she reacts to situations. Try and hint at things, rather than just say them outright.

I'll admit, this is really difficult, but if you work at it, you'll get better. And it might be kind of hard to understand what I mean. If you need help, let me know, and I can try messing around with a section of this (with your permission) to try and show you what I mean.

Anyway, before this drags on to long, the other main issue is pacing. You need to go through and look at how much time passes in-story for the various scenes, compared to how long they are on the page. The relationship between those two factors is going to determine a lot about how a scene feels. Some of them feel rushed, while others seem a bit drawn out. Try and strike a balance, but above all, be consistent, so the story seems to flow naturally, not speed up and slow down.

The last thing I'll mention is dialogue. I thought some of it sounded a bit unnatural. The best advice I have for this, given how "real" this story is, just think through it as though you were having a conversation. Think about what you would say if you were these people. Or, alternatively, go look at what you have and ask yourself if you'd ever say that, in that particular way. A lot of the time, it's just a word or two making the dialogue feel off, so just be thorough and stick with it. It's something that can be improved with practice, you'll get an ear for it if you do it enough.

So, there you have it. I can't think of much else that you're doing wrong. Those points go in order of importance, so the telling over showing issue is the biggest one. It's also one of the hardest things to get right, unfortunately. But give it a shot, even if it isn't perfect, anything moving towards that will be a step in the right direction.

Let me know if you have any questions, or need help with anything else.

Oh, wait, that's right, the ending, you wanted help with that. My advice? You haven't actually had any "action" in the story, just building tensions, so work in some kind of climax (it doesn't have to be anything crazy or flashy, just something to finish the story-arc.) Give the audience some kind of closure and a payoff for the time they invested in reading the story. Right now, you just kind of leave it hanging.