Second, apart from the lack of line-breaks, your grammar is a little too stiff - this is a teenager narrating in the first person. You have to try to get the sentence structure to scan like the kind of thing a nervous teenager would be saying.
Bolded parts are where I've changed words; although I've also deleted a fair number of them.
Heru_Tamago
Chapter 1
“Aijo”
I
headed for the door after the commotion
had passed. I was looking for
a cause of all the noise when
someone at the side of my house yelled, “You there! Stay right where you are.”
I turned to face him, terrified. I
didn't know what to do.
So I ran.
I
glanced over my shoulder. He was right on my tail! I had to pick up the pace. I gritted my teeth and sprinted ahead, gained at least fifty feet on him. I finally made it to the family’s safe house and I ducked in. Most of my family was already here, but my mother was missing. I'd lost the pursuit, but I feared that I had lost so much more.
I guess I should start from the beginning...
Your tense agreement was... disagreeing. Your grammar, as I said, was awkward. Your dramatic presentation wasn't. (Dramatic presentation is really a product of the other parts, though; once you get those right, the drama sort of inserts itself between the lines.)
To be honest, I think you need to do a lot more reading of what you consider good fiction (might I suggest popular authors such as Robinson, Pratchett and Gaiman for clever and fun fantasy writing, Niven or Anderson for speculative fiction, Abnett and McNeill for high space opera and parodic space opera respectively) and get a better idea of the... tone that they take. Each of course has his own style, and yours will be different from theirs, but there's something to be learned.
You need to have your style worked out before you can write successfully. It's good that you have your basic plot-line worked out, but that's only part of creating a working whole. The backbone, if you will. But as Ezekiel 37 tells you, the backbone isn't enough.