On Thu, 2 May 1996, Caroline Ann Seawright wrote:

That's because Ryouga thinks of her as a guy. Though he did nose bleed when
Ranma showed him her clevage... That's why he's not affected by onna Ranma,
either. If he thinks the person's a guy, then they're a guy to him... And
Ranma is Ryouga's most hated enemy, so how could he think of having a nose
bleed when this is the person he hates? Hate takes over from embarassment
there...

Speaking of nosebleeds, do they happen only to guys? Do they only happen 
when they see/think of something sexually explicite?