I blame the Ninja Gene.

Japanese women who duck and hide survive atomic bomb detonations, and pass on their genes.

Over time, other behaviors such as running toward the threat yelling, or taking pictures of the threat, or ripping open one's blouse when there is a threat, are selectively removed from the gene pool.

This also results in shorter Japanese women, who have less distance to travel when ducking and who are superior at hiding when ducking.

These five stars are property of Meerkat.

This doesn't account for the staggering Chinese population, who's first reaction to a threat is to take a picture of it.

I.... I'm pretty sure the Chinese weren't in the blast radius....
Like, either of them.

Stars for Meerkat.

Yeah there are completely different evolution pressures in China. For one, in China, there are so few women compared to men that women are effectively invulnerable. For the chance to get married, a man will gladly risk death to save a woman in danger. For another, rich Chinese men are much more attracted to interesting pictures than to "pretty" girls. So as you can see, the "Chinaman" has a very different society from the "Jap" even though they seem similar on the outside.

Jap girls are in constant fear of being raped, molested, attacked by a monster, or all of those.