It's funny because it's true. To be fair to Kasen though she's not the only one who goes around fucking a bunch of random guys and animals.
All of the other touhoes do that as well.

In doujinshi land, anything is possible.

they are not actually joking about the pig part i've seen her become a slave to one

There's a reason her nickname in the fandom is "lewd pink".

This is just unbelievably sad.

Stop Kasen bullying now