Kinda short wasn't it?
Expand it.  Go into Ryoga's specific feelings and expression (saying he
looks depressed doesn't mean anything, I've seen depressed people with no
expression, a smile, etc.)  expand on what happened the day that Akane
found out.  Was it a good day, was it the day he was going to confess to
Akane his love, was he surprised that he showed up at the Tendo's?  Go
more into the moment of the change itself.  Was he looking at Akane
lovingly as Ranma splashed him, what was Akane's expression before he was
splashed?  Go into the dynamics of the change itself.  this is a defining
moment in his life he should feel some sense of horror as it occurs.  Go
into Akane's expression.  describe her face don't tell us she looked
horrified that doesn't give us a clear image.  If you're going to have
Ryoga blow himself up have it take more than an instant.  He needs to
dredge out all the depression from his soul to do something that powerful,
streach it out a little more.

quesion:  is it Shi Shi Hokodan or Shi Chi Hokodan?  Most people spell it
the first way but I've seen it spelled the second way too.

Overall:  Good idea (it's been done before but so has everything else)  I
normally don't like to read darkfics because I don't like paying for
tissue but this could be a lot better.  It evoked no emotion from me
what so ever.  Make us care about the character (in this case Ryoga), give
us some history, some background, we need to know why this is happening,
what's going on, never assume your reader knows the story already, rehash
it from Ryoga's point of view make us see why he's so depressed.  Show
don't tell, it's much harder to feel for someone who looks depressed
rather than someone who's face is twisted in an expression of unspeakable
pain and agony.  His walk should be described (maybe as the shuffle of one
who bears a lifetime of pain but only looks the age of seventeen).  

It's a good outline for a fic.  As a darkfic it fails to reach it's
emotional potential.  Revise it a couple of times and send it back.

Thanx for listening to me rant and rave

AJ