Making a book
Hello who ever from Funimation is reading this I have a question. I plan on creating a book about anime coming to life and I was wondering if I could use some characters from your series. I plan on using characters from Highschool Dxd and Heaven's Lost Property. Again, I just want to be sure if it is okay with you before I start this book. I honestly have no idea if I'm going to try to get this published yet, but when I do I will tell you.
Someone at FUNi probably couldn't give you permission to do that… you would have to go to the original rights holders in Japan and they would not be likely to give you permission.
The best course would probably be to change them just a little bit, so that people who know them can recognize them ( ex. a beautiful red-haired demon girl who makes chess references and her name is Lia). You should look up the anime series Outbreak Company for good examples of that.
BTW, the probability of IP holders sharing rights of anything to anyone: 0%.
If you want to do something, just make it fan-fiction. Although technically considered non-legal, it is generally permitted by Intellectual Property holders as long as it is labeled as such, and not sold for profit.
In fact, we have an entire sub-forum dedicated to fanfiction right here on the forums. Feel free to post any stories you come up with (provided they are safe for work, that is). :)