What's the logic behind the nosebleed thing?

its just a comedy thing. ussually when someone is excited due to pervertedness it would show it. It's basically like blushing i guess. when a guy is turned on their **** goes crazy. Animes wouldn't show u the ****. Nosebleeds cover for it

It is a sort of way around certain censorship laws which Japan does have and for the Chinese Movie maybe they just copied it do not know on that score.

It goes with the theory of arousal causing blood to rush to both male heads the little and big head in guys. Well as it is they can not show a male erection in non-hentai Anime meaning since when a person blushes it is blood rushing or sometimes getting hot making a person blush and as an erection is a lot of blood rushing to the little head an erection in their opinion is a lot of blood rushing to the big head as another way to show it problem being you nose has holes allowing blood to escape.

Its an old wives tale in Japan. When a person gets aroused their blood persure goes up. The heighted blood pressure then causes the nose bleed. This does not actually happen in real life, but it is really funny. X )

High Blood Pressure!! Guy sees something perverted which turns him on. What happens when a guy gets turned on? Well in order to get his junk to "function" it has to raise the Blood pressure. Which is why in real life, High Blood Pressure Medicine, will cause E.D. mmhmm.

Usually it causes excitment, which can make some people nose to bleed. It's a medical condition.

because of the hotness

I never heard of it lol