Sword Heart
In the world where a gigantic sword fell from the sky and changed everything, certain rules could never be broken. Still, every rule is bound to have its own exceptions. The ability to surmount the wall between each Swordsman grade, also known as 'Sword Heart', was such an exception.
Coined with this specific name by his master, this was the cheat ability that Ray, the world's protagonist, had received as the culmination of his previous life's experience as a Sword Master. Not only did this ability enable him to fight Swordsmen above his grade by raising his Sword Breath's quality, but it was also influenced by his emotions, making it very suitable to use as a 'plot armor'.
Unfortunately, this was as far as this world's exceptions went. For the rest of the Swordsman, having no less than a grade that's equal to your opponent's was a must, otherwise, not even a Sword Breath cover could prevent their sword's predetermined destruction and get reduced to normal humans.