It never ceases to amaze me how these stories trivialize mortal foes, and the actions of other people in the world.
That "terrible demon" "had" to be sealed within a sword since, apparently, he couldn't be destroyed, not even by a sword-saint.
And then the MC destroys him, using the abilities he got from an existing sword-saint.
A story about an overpowered character, lacking any tension in the actual fights, needs something else to bring the story along. And this story is god damn funny. Thanks for the translation.