Board Thread:Questions and Answers/@comment-104.254.70.98-20190103015633/@comment-46142448-20200621200608

The current Demon Lord, and source for the monster girls' forms and desires, is a succubus. A very powerful succubus, but a succubus nonetheless. Thus, the sexual desire for human males comes from the nature of a succubus. Keep this in mind.

One of the main underlying desires for monster girls pursuing human men is the desire to reproduce. While it is stated in setting material that a monster can undo castration and similar things, if a male's genitals are not yet developed to a reproductive state, he can't provide that desire for the monster.

Second, monster girls desire the "spiritual energy" from semen as sustenance. As most myths and religions that regard semen as a spiritual thing associate that to the reproductive capacity of the sperm, it would stand to reason that too young of a male wouldn't provide substantial spiritual energy for a monster.

Third, we go to one of the two cultural origins of the succubus myth - wet dreams. Which generally don't happen until puberty. As MGE tends to base things on analagous imagery, I take this, with the prior two points and the aforementioned succubus nature, to mean that monster girls wouldn't have their supernatural attraction to any prepubescent male, at the very least.