After the break. Not being funny, but to say Ninja Gaiden was an "influence" on this is putting it mildly.
There are three videos there. The majority of the first one's an inventory screen, from the look of it. The second one's fighting. The third one's the ninja sliding down the side of a building and fighting a massive spider while doing QTEs.
Seriously, his hat even looks the same. See for yourself. Thanks, Blerk.