Few animes come even close to Elfen Lied's story (or brutality, or exquisite ecchiness for that matter), and considering that the original manga it's based on was only completed in 2005 - with the anime adaptation airing in 2004 - we can certainly hope we'll see more of it in a sequel. Elfen Lied 2 is, after all, the most yearned-for anime sequel in our current poll.
But that's not what this story is about, unfortunately. The only reason I mentioned it is that the author of Elfen Lied, Rin Okamoto (a.k.a. Lynn Okamoto) has released his (yes it's a "he", despite the misleading name) collection of short stories, titled Flip Flap. More info about it, via AkibaBlog, after this cover pic.
"It's a set of 2 books, and they include manga that Rin Okamoto wrote for the first time, unpublished stories, etc. (...) An old man who can change the memories of people, a genius pianist who gets a handicap on hands, a girl who has only few days to live, etc, many kinds of characters are caught up in a tragedy and a comedy! (...) Sometimes, it's comical, sometimes, it's grotesque: always sad but somehow it's warm."
Rin Okamoto himself is also quoted with the following comment about this Flip Flap collection, which apparently includes a couple of stories that he didn't want to be included... and not because they were too warm and fuzzy...
"I myself can't even look the 2 stories that are unpublished. I saw those stories after 7-8 years, and I was like "oh nooooooooo!!" after just looking at first few pages. So I couldn't check anymore. But I knew I had to check them, so I tried. Then soon, I became "oh nooooooooo!!" again. I asked the person in charge not to include those 2 stories, but it didn't work. Now, those are in the book, but I still can not open the one whose color is blue. When I riffle through the pages, I again become "oh nooooooooo!!""