>>29182131I think it's because some girls are so cute that they are fascinating.
You can't stop thinking about how insanely cute they are and how the idea of them pooping or having smelly feet doesn't seem realistic at all. You know it's the truth, but their cuteness prevents you from even imagining it.
Chicken-chan has a cute face, an adorable loli voice and a charming personality. On top of that, her outfit is really cool. It's hard to imagine her doing something disgusting or embarrassing, because on the outside she's literally perfect. There's an aura of perfection around her!
Seeing her doing something that humanizes her and ruins that perfect girl image would be like witnessing real magic. When you see someone farting, it's disgusting. But Chicken-chan could literally push a huge turd out her ass without it being gross. The shock from seeing something so unbelievable, almost magical, would be stronger than the disgust you are supposed to feel.
And the arousal comes from the fact that it's something embarrassing that she doesn't want you to see. She's being humiliated and degraded because someone is watching her taking a shit! Her public image as a perfect, unreachable, outgoing, likable, super dank loli girl has been broken into millions of pieces! She's now exposed and vulnerable!
You can look back at every moment you spent with her catching pokemon and battling, every cute smile and expression... And you can twist all those memories into something perverted, because now you know what her nude body looked like, you know what her farts sound like, you have seen what she tried to hide with all her might.