There are unused voice files within the game, suggesting that the game was originally going to feature a tag battle mode. This game mode did not make it into the final game.
Rachel's Break Blow is based on her "Blades of the Ouroboros" spell from Ninja Gaiden Σ.
Momiji's Break Blow is based on her "Art of the Crimson Lotus" ninpo spell from Ninja Gaiden Σ2.
Ayane's Break Blow is base on a ninpo attack she performed in a hidden cutscene from Dead or Alive 2.
The Memorial stage is directly underneath the DOA Colosseum. This stage is only playable in the story mode and cannot be accessed through the other arena.
According to Tom Lee, Diego was created largely to give representation to the Hispanic community in America as well as appeal to American sensibilities.
NiCO was originally intended to be Russian, and her Japanese voice actress Sumire Uesaka was originally chosen for her Russian language skills. However, after changing NiCO to be Finnish, Uesaka's language skills ended up not being put to use.
NiCO was designed to appeal to fans of anime and Japanese light novels. Her fighting style was inspired by Penchak-Silat (an Indonesian martial art), and director Yohei Shimbori was inspired by the 2011 film The Raid to implement this fighting style into a fighting game.