Ninja Gaiden 3 will contain a code for an exclusive demo of Dead or Alive 5 but depending on whether you're a 360 user or a PS3 user you'll get a different exclusive demo. Both consoles with have access to two characters; the 360 version contains Hayabusa and Hitomi, the PS3 version will let you play as Hayate and Ayane. If you want all four characters you'll have to buy the Ninja Gaiden 3 collectors edition which will give you access to the premium version of the demo.
Andriasang reports that there won't be a demo for the game available for free, although that might be changed after Ninja Gaiden 3's release and the lure of these demos is no longer applicable…