On the contrary i feel it's not incoherent at all.
It has lots of absurd situations and everyone is a weirdo, but they keep the world and characters coherent while regularly adding new stuff and that's no small feat..
@Tolorin : the same way you did with your parents/school as a baby. You designate objects or mimic actions and learn the sounds, and try to build up from there.
NotAHat's headcanon can be a good explanation, but i don't feel like going through those extrasteps :p
I kinda want to stop reading this cause i spend most of each chapter thinking "put some fucking effort into learning the language you idiot !". MC is already the usual shy/dense protag type, adding that lack of progress on the fucking most obvious step to take to improve his situation just makes...