I don't see a katana, shuriken, nunchukus, or even caltrops included. No cool weapons at all. Is it possible you're using "ninja" as a brand name, while shortchanging us on the danger front?
I suppose you could body-slam someone with that sleeve. But it probably wouldn't hurt them, unless the visible accessories were included. Which they might be - you forgot the standard disclaimer.
Maybe the gold pen is a disguised poison dart blowtube. Or those items in the mesh are brass knuckles rather than keys. Though brass knuckles really belong with the forthcoming Gangster Sleeve.