Interesting, I think given the scope of the story, this should be a multi-chapter story, but an oneshot works too, even if everything seems to be too rushed ("I should have loaded this with more than one bullet" - that was an actually funny line) and you could space the paragraphs.

But I really liked how their personalities changed a while and yet stayed the same, Saki being moé and Akira still being kind (only him to befriend a mutant girl he just met), and the swap was interesting.