Salem said: Probably because animal usually don't show emotion and just get things done.
Cats definitely enjoy tormenting and playing with their catches. I saw many times how they played with mice, letting it run away a bit, and then catching it again, tossing into air, tearing limbs off, before finally eating it.
It was anon's work, you can see it in the drawings. He put the Alice there, and stole the Reimu's surviving baby, and (I think?) he punished that Reimu by sewing her mouth shut and sewing her butthole shut with the baby. Pretty neat and creative if you ask me.