Ninja Gaiden 4 is the perfect place to jump into the series
TL;DR
Ninja Gaiden 4 features a new protagonist, Yakumo, making it an ideal entry point for newcomers to the series, especially for those who missed earlier games.

When the first 3D Ninja Gaiden came out on Xbox in 2004, I really wanted to play it; though the game looks a little antiquated now, at the time, teenage me thought that ninja protagonist Ryu Hayabusa was cool as hell. But alas, I didn't have an Xbox, and I don't think I could have convinced my parents to let me get such a (for the time) violent game. Even as an adult that could buy whatever game I wanted, I never got around to playing the franchise. Twenty-one years later, I've finally scratched that itch.
Ninja Gaiden 4 stars a new character named Yakumo instead of Ryu. Yakumo is a total punk; imagine someone with the short, unaffected per …