It started as a cute funny conic of a child who is found of his older neighbor But as the time passes the manga starts to take a darker turn as how Tsubaki (the child) wants to be in actual relationship with his yuu-nii... He was innocent at first just wanted to impress and protect his big bro but his friends encourage him to do lewd stuff in order to get yuu to love him .. Children should enjoy their childhood and not be thinking of these stuff So normalizing this is a big mistake It's like an inverse pedophilia Also it would be actual pedophilia if yuu fell fortsubaki.

You'd think im exaggerating but in the future if that became to our real life it'd be so messed up since children are still learning the basics and someone coud deceive them with fails information or take advantage of their pure feelings.

So don't let the cute art style get you.