One of the new modes is 'Tag Mission,' which allows players to switch between two ninja heroes on the fly, swapping in and out as they see fit. On the ninja heroes front, the three ninja ladies of Ayane, Momiji, and Rachel all get newly designed costumes in Plus 2.
The other new mode is 'Ninja Race,' which really is as it sounds. The twist is a sort of Ninja Gaiden take on Mario Kart, in that you can collect items and take down enemies to increase speed and attack power. Unlike Mario Kart, though, there's no indication it can be played outside of single-player.
It also seems much of the Vita-specific functionality is returning from Ninja Gaiden Sigma Plus, with Tecmo describing touchscreen and Sixaxis controls that very much sound like the first game's gyroscopic first-person aiming. The easier 'Hero' difficulty also makes a comeback in Plus 2, which is scheduled to release in Q1 2013. %Gallery-172781%