While I get the feeling of a slice of like from this manga, much like Barakamon, I'd like to know what to expect in the later chapters. And TBH a subtle romance is the best thing in these slice of life kinda manga.
So, Is there any relationships between the characters of this manga?

No, there are no romantic themes whatsoever in this manga, just hilarious Yotsuba-themed hijinks, easily one of my most favorite manga (and I'm mostly a romance/drama fan, which should tell you just how great this one is) 🙂

Nope. None at all, bless Kiyohiko Azuma! If you want romance there are, like, hundreds of other translated slice-of-life manga out there (with or without kids).