When I started reading this, it seemed a bit odd, as I've heard of
Tourette's Syndrome, but not exactly what it was. I got the general
gist of it over the course of the story however, and afterwards
looked it up. My first read through gave the impression that those
with the syndrome aren't aware of the fact that they're making any
noise, or moving in any way when it's involuntary. However, from
what I read afterwards, that isn't the case.
This presents a problem with Kasumi being true to canon, I can see
her trying to ignore the symptoms, but when Ukyou comes in and
actively asks why she's swearing at her, I think she would probably
give her an answer. The side effects of the medications I read
about do at least tailor rather well with the traditional portrayal
of Kasumi, though :) Aside from the fact that none are completely
successful in inhibiting the TS.
At any rate, it was an interesting story, and though some of the
humor fell flat for me, other parts of it, such as the confusion near
the end about Ukyou and the disease were rather amusing. If you could
manage to avoid the issue of Ukyou learning that Kasumi has Tourette's
Syndrome a little differently, I think it would come off rather well.