i'll be real. aside from like full anthro style art (as in, animal shaped faces) i have always seen four ears when it comes to human faces with animal characteristics. and everywhere people are like - why is it four ears again? but like, where are y'all getting this idea from? (aside from that one tumblr post i vaguely remember that was questioning how hearing works with 4 ears) asking seriously btw.
Ive definitely seen works with just animal ears though i dont remember much about them now.
But if you really want an example there is genshin, they make it so that their hair covers where human ears usually are.
When it comes to anime most kemonomimi characters (human characters with animal parts mostly ears and tails) are drawn with only two ears usually covering the human ears part with hair and we really see characters with 4 ears, Inuyasha and Yoko Kurama are great examples so seeing characters with four ears in manhwas is a little weird
I really don't get how these authors brains work! I know this is fiction but what's the logic in having two pairs of ears? When the ears of their animal side appears the human ears should disappear