
This is actually better explained in the novel about the whole "fated pair" thingie and how it functions in this world and it gets WAAAYYY weirder lol
Chika has kids and at least two of them have their "pair" life partner identified as infants
But I guess the only way I'll try to explain is that it is just more of an innate attraction or way of identifying their fated life partner and that there's really no intention of doing anything sexual until that partner comes of age and waiting isn't an issue because the beastmen age differently (so the age of adults in this world is 15) and live much longer so age gaps are more normalized
But essentially, as a piece of fiction intended to be read by people in this reality, the comic is shotacon and so is the novel it's based on (regardless of mental or physical age)
The only thing that might separate it is that it's very careful in writing so as not to feel exploitative and to respect the autonomy of concerned parties.

https://novel18.syosetu.com/n8953dk/
I only have this link and it's in Japanese. I don't know if it's translated anywhere but I've considered translating it myself for a while . . .
Anyway, I don't know if your phone/browser will auto translate the thing for you like mine does but I find that the Google translated version isn't too difficult to read and actually has some neat characteristics that I feel fully translated works miss out on
Anyway sorry, I'm rambling but I hope this works for you

This is a better translation. https://blsnacks.wordpress.com/ai-wo-ataeru-kemenotachi/
they thought he was 10 but were still attracted to him, feels insane but then again this universe has legalised slavery so what can i say.