i think you were thinking of inu yasha's tetsaiga that could kill a thousand enemies in one strike sesshomaru had the healing blade tensega
And if he upgraded it even furthermore.. It could compete even against Sesshomaru's Demonic Strike from InuYasha anime, who could destroy hundreds and even a thousand demons with a single strike of his sword.
The characters names aren't translated accurately enough to know who's who and where and how they fit into the story and what their role is supposed to be in regards to the plot and just the world in general