To install:

You must have the Unpack Dark Souls for Modding tool. https://www.nexusmods.com/darksouls/mods/1304

Once you have run it and unpacked the game files, move the "parts" file from the zip into the Dark Souls PTDE DATA folder, approving any messages about replacing files. 

If you want to remove the mod, delete all files starting with "WP_A_0402", "WP_A_0450", "WP_A_0451", "WP_A_0452" except any files ending with ".bak" Then, rename each .bak file, deleteing ".bak" to leave the original backup file.

Ex: "W_A_0451_L.partsbnd.bak" becomes "W_A_0451_L.partsbnd"

The models replace: 
-The Uchigatana with Virtuous Contract
-The Iato with Cruel Oath
-The Washing Pole with Virtuous Treaty
-The Chaos Blade with Cruel Blood Oath

Thanks so much to Meowmaritus for their DSFBX tool ( https://github.com/Meowmaritus/DSFBX ).
Weapons from Source Filmmaker Workshop, user Mikey {Jaw}