This isn't bad. Personally I prefer seeing Natsume and Naomi as an item, but obviously that's not the sole interpretation.
I'll admit that I don't particularly care for how differently Hisao acts in the beginning; like forgetmenot, I've probably read "Enter Stage Left" a thousand times, so his different demeanor here was more jarring than refreshing. I think this chapter was something you needed to get out of your system—something of a warm-up to writing the rest of the fic—but I can already tell that once you've got a few more chapters under your belt, you might want to discard this first scene entirely. We've already seen it, basically, and I think you can safely start in medias res without getting anybody confused.
Here's a bit of advice—Hisao is the most interesting when the girl he's in love with rubs off on him. He's a notably different person in each of the five routes (and in the Shizune bad end, in microcosm.) To have him
start off unfamiliarly kind of steals Naomi's thunder. Speaking metacontextually, it's not
your job to change Hisao; it's
Naomi's.
One more thing:
I force the stiff uniform on, noting the little brown-devil of a scar, crossing my sternum angrily, tie the... tie... and put on my shoes.
If you mean that Hisao is putting on the Yamaku school uniform, you've made a mistake. On day one, Hisao wears the uniform of his old school, which we never get a chance to see. It isn't until the morning of day two that he puts on the Yamaku uniform his parents left in the dorm room.
This is why Iwanako still wears her old school uniform at Yamaku in
Mean Time to Breakdown: she entered her dorm room only to find out that the school was totally out of uniforms in her size.