I liked this. Very depressing. Also makes some good points: there are
some demons you can't fight with fists.
The only thing I'm not sure I like is the ending; that is, Ranma being
female, laughing at the wedding, cutting off his pigtail. The killing
himself part is fine (er, in context of the story, I mean.) Maybe you
could have a couple of paragraphs at the end describing Ranma's suicide;
that would be terrible (in a good way).
Oh, small point: lots of kids die of cancer, 18 isn't that young.
Loved the story. Now I'm going to be all depressed for hours, which is
the mark of a good story. :( :)