Lol, why everyone freak out ? Yall too focus on the fact that she is yonger. But this is like the most legal than what happen to this manga, compare to the main pair.
It was a cheek kiss, and little kids talk about romance and crush is not unhear off, No sane parent gonna freak out over that. And it not like they gonna have sex and shit.
I swear if take this pair out of context (this manga) and show it to some of my neighbor, who are not anime/manga reader of course, they wont feel like anything wrong with it.
It was unrealistic how they act, maybe. But then Chihiro was even more pure out of the two judge from 2 chapter ago