Here is my translation and fix of the Ninja mod, that I got from the Japanese Wiki.
It adds lots of neat stuff.
A decoy that you make that is like a scarecrow that zombies attack, a jetpack, shurikens, insane new martial arts (one that creates after images of you - using Lua), Kawasaki Ninjas, a note that when you read it turns out to be a kill list with YOUR name on it, yakuza tattoo mutations, cosplay ninjas, vehicle mounted automatic fold-able shuriken throwers and lots lots more.
I couldn’t get the 16 overmap tile Ninja Tower of death to load yet, unfortunately. Please let me know if I missed anything that needs translating, or if anything isn’t working.