Basically a way to roast flat chested girls (but please don't do that unless you both aren't good friends)
Flat girl: Omg you're so fat you need some touch grass fr fr
Fat boy: At least I'm not built like a fucking airport lane
*Gets smacked to oblivion*
English: Buhi Buhi
A squealing sound made by pigs, but often in hentais it was often used by girls that were corrupted by sex/netorare.
Therefore they make this sound to express pleasure to their master.
NTR man: Look, I'm going to cum in your pussy Nobuko-chan!! Raise your ass and say ãããã!!!!!
Nobuko: ãããã~~~~!!!!!!!!!!
(Fucking cums)