Looks like Haruto managed to cockblock himself by not allowing the true reason for the question to get through.
I did find some other explanations for cat faces though::
猫被り(Neko-kaburi);Make one’s face like a kitty. - English ; a put-on; fake modesty; feigned ignorance.
Neko wo kaburu. (猫を被る。)- Literally it means wearing a cat (like wearing a cat costume / mask), but it’s like saying “butter wouldn’t melt in his / her mouth”.
猫を被る -wear a cat (konekono-heya) - A wolf in a sheep’s clothing, feign innocence, hide one’s true self. One more example, beautiful rose always comes with thrones. You want to be very careful with someone who looks so cute and talks so smooth, she or he may might trying to get something from you…
..I was actually looking for another saying (which was about revealing truths), but this one about pretend innocence seems so much more likely that I gotta tag in
@BlackHandScans over it just because.
And since I put in the tag I also gotta add: Thank you for your hard work.