I was personally awed by the plot. I guess I'm not used to long and detailed military styled kinetic novels. That's a good thing, by the way. The story is detailed, though lacking in a few areas, and it is an amazing accomplishment for a one-person project, and for your first visual novel. Well, there is hardly any spoilers in my comments, but for safety's sake...
Things to improve on (in my opinion... I'm terribly sorry if they hurt your feelings. I think that it's a good thing to point out mistakes, so that artists and writers etc. can improve and such.)
-Although the sound effects were good(I got a little scare, though, perhaps my volume was too loud, when I first heard the sound effects. Probably due to the suddenness too, for there were no music), I think it would be good to add some music if you could, though you've mentioned the reason for not having it.
-As mentioned, there were some overlapping of character sprites(that's what you call them, right?)
-Very minor spelling errors
-The main character seems a little passive emotion-wise. This is not really a bad thing, and this makes the story more realistic, giving the character her own personality, but it makes it harder to relate to her
-Some details of the story should have been further elaborated on, such as the death of Chris, Rachelle's parents[especially her father], the relationship between Pierce and Terrence, the relationship between Milana and Terrence, Terrence's background story, the existence of magic and blood runes, why did Crispin kill Terrence's brother, Josh's attachment to Rose, how did Rachelle continue training after the "shooting competition", perhaps even why Iris is so obsessed with guys, etc.
-Perhaps you could cut down on the characters? While I agree that they all play an important role, having too many characters means focusing less on them as individuals. (FORGETFUL ME TENDS TO FORGET NAMES OF PEOPLE WHO DON'T APPEAR SO MUCH, so I had to note them down ._.)
The Good Points (in my opinion)
+None of the bad points really affected the overall plot and such
+If you did the backgrounds by yourself, I'd have to applaud you
+Presence of sound effects
+Originality
+While the plot may seem rushed in instances, I liked the fact that you didn't jump straight into the war, and touch on how Rachelle got along with her acquaintances
+The plot was quite detailed. Haha, this is like a repetition of my earlier comments. Due to tiny twists, the long(well, long for me) story was kept interesting, and grabbed the reader(well, "my") attention. That's a good thing, because lazy people like me who gets bored easily will stop within the first few chapters
+You had chapters with a title. This gives a sense of suspense to the audience.
+It was rather realistic. Although it seems that the main protagonists somehow happens to keep running into each other, on a second read, there were time lapses between their meetings, and it was over a long period that their relationship grew.
+Hints of character development
+The characters have PERSONALITY. ***
So... anyway, good job, and I look forward to you making more VNs. If anyone is somehow displeased by my remarks, I sincerely apologize. I will take this down if you're offended somehow. BTW, this is out of curiosity, have you had experience in the military? *phew* This is the first time I've typed so much in a forum..