Oh geez. Time to put on the logic cap yeah?
In terms of biology... ok, wait, gotta preface this with the obvious:
Most likely the author didn't think too hard on this. It is most likely "Haha, funny moments" and just left it at that. I really doubt author-kun actually thought about it seriously.
Anyways.
Biologically speaking, I really doubt that there is anything OVERT or measurable differences between Baseline Modern Female (Real) and Baseline Modern Female (Fantasy). There is no "magical organ" or a biological mutation that would make for a hyper sexual female that is different between the two.
Biologically speaking, both "Real" and "Fantasy" most likely have the same average sexual drive potential. There do be some very horny females in the "Real" world.
The difference between the two (and this also extends to the males of the "Fantasy" world) is the circumstances of their society and the mental drive.
I've already listed out some examples of the societal differences and how it affects the dynamics of the female-male relationships and how it got driven to the point in which the "Fantasy" world relies on Artificial Insemination and the mandatory semen donation from males. If you guys want to read into it, I had a rant on it and I can provide it if needed.
This also ties to the whole "Mental Aspect" of it. In terms of the Fantasy Females, it really does drive the whole stew in terms of achieving a biological and societal "victory" by securing for themselves a source of semen. This is not only supported by the government both in policy (assumably) and financially , but can be (assumably) seen as a higher social status of achieving something as "exclusive" of getting pregnant via actual sex.
That is nothing to say in terms of the pleasure derived and the endorphin hits on climax from sex.
Add to the fact that MC-kun really isn't good at hiding sh-t and you'll get females who are like them when confronted with such a heady smell. Most likely it triggers brain chemicals and stuff like that but, again, there isn't anything OVERT going on that is different between the two kinds of females.
In terms of the boys.
Biologically speaking, just like the females, the boys themselves have the same sexual drive potential between the two.
Just like the females, I have already laid out the societal circumstances as to what shaped the boys into being what they are in this world. As an emphatic being, I might not be able to directly relate to them, but it is quite horrifying when thinking of the potential circumstances that befallen this fantasy version of the human race. It is at the aforementioned rant. Again, I can provide if requested.
As noted at the semen bank and the amount given by MC-kun vs Other males, MC-kun is able to provide many portions of semen compared to other males. This is all down to "motivation". In terms of the fantasy males, this kind of thing is a mandatory act of donation for them. Presumably, this is imposed at the very start of them being able to provide "live semen". Society as a whole functions when you have citizens that makes up that society.
If you need to, you will have to force it, even if it might not make them happy.
That's the circumstances that they lie on. Would anyone be motivated to do it when, at the first positive result of "live semen", you have to donate your semen at some facility like clock work? I believe it is every month?
It is like eating the same thing over and over again. You get sick of it. Tie that with the whole thing about sexual relations with females being this universally traumatic thing for the fantasy males, anything "sexual" that involves these circumstances will be... well... avoided by the party involved (in this case, Fantasy Males) and will not be very motivated to actually participate in it.
MC-kun on the other hand is "very motivated" because he is not raised in such circumstances. Add to the fact that he also engages in regular exercise (which presumably other males rarely do beyond the very bare minimum... why would they? They actually DO NOT WANT female attention on themselves...) and you'll have a physically healthier male in MC-kun. This in turn would allow for a higher ceiling for sexual potential.... etc etc.
Basically: There ain't no biological differences between the Fantasy Humans and Real Humans. It is all down to other factors like societal and mental.
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So this is an adult that can control themselves... I wonder where she went to school... maybe an elite school?
12 pages and I assume the JP had lines in JP that are typical in zombie flicks.
Thanks for the TL!