Double post for Great Justice!
In Zelda Spirit Tracks there is a little village at the sea completely inhabited by women. The reason for this is because the men of the village didn't listen to the (female) fortuneteller of the village, and went fishing even though she predicted that something awful will happen if they did. Looks like she got last laugh, since all the men got kidnapped by pirates during fishing. So now the village is all female.
This got me thinking. During the Lunar Invasion, lead by Yukari to teach the youkai a lesson, did Yukari infact send all the male youkai to the war, and thus they're inevitable doom? Perhaps the males were seeking global conquest and power, and Yukari got sick of it, so she send them to a place where they'll either ger slaughtered or captured for all eternity. Thus, there are almost no male youkai left in Gensokyo, with the remaining youkai almost all being (relatively) young females.
An interesting notion, no?