What makes female rookies attractive?

[Lilamon]

Despite what they are called in the Japanese Anime, I think it's an insult to consider Agumon and the like the same as human children. We aren't talking about naive youngsters who don't know the difference between right and wrong. They're smart enough to launch tactical attacks (as seen several times in the series), take care of themselves, etc. I've never once viewed them as children.

Not as in Human Children. More like the young forms of powerfull monsters. You know, like Godzilla Junior ( Heisei ), who is still not fully grown, but will kick your ass.
Same for Child-Level Digimon.

In fact, I'm working on a romance fic involving a boy and his female partner that doesn't involve inflation in the slightest.

Sounds fine to me.

And to clarify, when I say attracted to, I don't automatically mean sex. A guy can find a girl to be pretty and still not want to sex with her.

Wouldn't that be another form of finding someone attractive?