Hmm... first off, NEVER touch the blade with your bare hands. Aside from being highly disrespectful, it could also destroy the blade and cut you up pretty badly. Clean cloth gloves should work. Second, is it an old sword? A WWII blade? Paul Chen, Paul Champaigne? Was it handmade or factory-made? Do you know the metal it's made out of? Does the tang have a signature? If so, could you scan or email it to me?
Sorry for all the questions, but the age, metal, etc. are important in determining care, in that if you have an aluminum blade you don't clean a traditional cleaning kit, etc....
How did you come upon a katana anyways?