Yaiba: Ninja Gaiden Z has a bonus mode called 'Ninja Gaiden Z.' It pays tribute to the NES original and sees you hacking up zombies in a 2D scrolling beat-em-up fashion. Tecmo Koei's released a video of it online. Watch it here.
The publisher has explained that the mode is unlocke as you play through the core campaign, and comes with a brutal, old-school difficulty curve.
Yaiba: Ninja Gaiden Z will drop March 4, 2014 for PS3, Xbox 360, and PC in North America, and then across Europe from February 28.