This idea is free to anyone. You do not need to contact me to ask if it is alright for you to do this story or that. I will likely not be on this specific account often, so contacting me about this is not something I'd advise. Use it to inspire your own ideas, or take it and make it your own.
Kamen Rider OOO X Naruto:
Plot: Taking place at the end of OOOs, Eiji and Ankh are sucked into the black hole along with the Kyouryu (dinosaur) Greeed/Maki. (Spoilers if you have not seen megamax) Instead of being transferred to the future, they're transferred to Naruto's world. The metals are scattered across the nation and Eiji has lost the OOOs Driver. He searches for the driver along with Ankh while the driver gets some new users.
Conditions:
Preferably before Part II of Naruto, but if this idea gets you more interesting ideas, go for whichever, Part I or II.
The previous greeeds, Uva, Kazari, Gamel, Mezool make their return as "arms" like Ankh. Be creative with how they return.
Since the Naruto World is brimming with desire, no one character there can reasonably pull off what Eiji has done by withstanding all the combo forms and using it as he did. So this is what "new users" meant. This driver is going to passed around. Explain how the driver is able to be used by more than one person. Have fun with how it's passed around, but a must is that all of team 7 must have used it at some point.
In order to use combos, the one using the driver has to be possessed by the respective greed. (Example: Naruto wants to use Gatakiriba, Uva would have to possess his body in order for him to do so). Have fun with all of that obvious interaction with the various greeeds and characters.
Come up with some unique way or reason for their need to use the driver, as oppose to strong ninjutsu.
At some point Eiji encounters team 7 and asks for the driver back and of course, incidentally shows of being able to use multiple combos without becoming too tired.
As a show of Naruto's growth and despair, come up with a unique way in which is own desire brings birth to new Evil Greeeds.
Neutral Kyuubi, or rude/evil. Anti-hero/Rouge to sum things up. No nice Kyuubi. Gender of the kyuubi is up to you. Also included is reasonable interaction between him and Naruto. Not too much, not too little. Staying true to the series depending on the part, they don't talk a lot on friendly terms, so keep it true.
Ankh's medal does not break, but remains very much damaged. Ankh is in a specter form or possesses a shinobi (make it interesting, if you want.)
Pairings up to you
Reason for this story?: I'm seeing a lot of crossovers, but none or not many of them are true attempts at crossovers. I'm seeing more "Descendant of ", "Discovering drivers", or other kinds of story that in my opinion are more fusion like stories and not really a crossover.
Why I'm not doing this myself considering the amount of conditions?: The main reason is that I've lost my muse to want to write things further beyond just a layout of ideas and conditions. Writing fanfiction is no longer an interest I hold. Also, I like Naruto, but I don't like it to the point that I know enough or want to know enough about it to give it justice and write about it. You could say that I hate it and like it. One rule about fanfiction second to writing for fun is that you got to truly be into the subjects your writing about. I'm really into OOOs and know a good amount of how things work, but I don't like Naruto the same way.
So take this story and make it your own. I'd like that the conditions be followed or considered in following close as possible, but not everyone may see things in similar light like myself, so like I said; use the challenge/idea to inspire your own ideas, or take this one and go with it. Hope someone takes up the story or idea and makes something interesting out of it.
XaiRider