The original I-Ninja is an underrated action game that was developed by Argonaut Games and released for the Xbox, Playstation 2 and GameCube at the end of 2003. The works on the sequel were started after a few months, but sadly the studio had some economic problems and they had to closed down in October 2004. I-Ninja 2 was never officially announced: only some concept arts remain as a memento of the project.
From the looks of these arts, it seems that the sequel would have been set in the same setting as the original I-Ninja, with a scenario that mixed ancient Japan and futuristc robots, with even more crazier and hardest levels to play in.
Thanks a lot to Tanguy for the contribution!