
if you haven't read it yet, try this! https://www.mangago.zone/read-manga/i_became_the_youngest_sister_in_law_of_the_male_leads_in_a_tragic_reverse_harem/
i think you'll like it based on your comment. the kid MC here really gets to act like a kid and it's so cute. (=・ω・=)

That's actually a fascinating question.
I think for South Korean isekai maybe it has to do with the pressure on children from a very young age to 'stand out'.
Attending tutor academies after school and if you're doing something extracurricular, that could take up a child's whole weekend or force them to wake up even earlier to participate.
So if you have an 'edge' i.e. knowledge of the novel and market trends, then it becomes almost lazy(?), wasteful(?) to not use it for one's benefit?
Lulu is the cutest and luckiest girl in the world, I even really like this family and story, but at least please, why are the stories I'm reading lately... About reincarnation, especially if they become children, always and almost all of them are underage and already working, starting businesses, or, even worse, directly becoming the head of the family. It is true that what possessed the little child in a story is a grown woman, of course I understand their thinking is far from that of a little child. But when they possess the bodies of small children, can't they do things like ordinary small children, until they're old enough? I mean, isn't that a normal thing to do? Because everyone who goes to the isekai world, they are people who suffered in their original lives, and start a new life with a better life., but why do they still have to waste their childhood even after being in another world... But again, it's just my curiosity, why do many writers create stories like the one I described above... Just curious.( ̄∇ ̄")