I think it's from a doujin game called "Asobi ni Iku yo! Cats Attacks!", which it is based on the anime "Asobi ni Iku yo!" (rather moderate story, but at least good animation quality and -most important- neko girls :)
she's having sex with the whole world? epic! i wonder what she'll give birth to after this xD but i think more probably the world will shatter in pieces during the act...
the end of the world as a great sex ride with a mastodontic neko girl! maya guys, eat this!
