Badges update automatically and link to the resource pack page on MineUniverse.
"I am sure this katana would be happy to have you as its master"
Make sure you either
A. use Optifine with Video Settings > Quality > Custom Items: ON or
B. install the CIT resewn mod
Install the ressource Pack and rename any Sword to "Shusui" using an anvil.
Enjoy!
little bonus, while holding your shusui in the leftmost slot, take your helmet off and try this command:
/item replace entity @p armor.head from entity @p container.0
(other swords might follow)
(I made this for fun, I have no rights for the visuals and names)