A (tail) vore/unbirth doujin. I don't even know.

Artist pixiv: http://www.pixiv.net/member.php?id=598217

Hmm, to think that other girl was able to attach a monster penis to herself, and eat and transfer the other girl tail to herself, am I crazy or is she a better demon than her!!!

Base +4, zeke666 +7

Since she always ends up unbirthing, I think that Kyouko should not wear panties. That's a time she'll lose and it might have been critical.
The one that KamikazeShooter says, is one of the people that bullied Kyouko before turning into a girl, she ate them, and after nourishing of them, she changes their shape, before spitting them out again. The monster is what was still left of one of them.
(The very first chapter of this character, (not this manga) is https://e-hentai.org/g/734561/dedcec58b4/)

Base +5

I am slowly translating this to english (sorry I'm very busy right now) as I have with this artists other works, if you want to check them click my username.

Base +6, Jikreek +15