>>1388778That's not what edge is, katanas and almost every other Japanese sword of the past had a single edge, it's just how they forged stuff. A "double edged katana" is a modern invention that doesn't fit the original description of the sword and requires a different forging process.
There isn't such a thing as a "blunt edge" which could be what you're thinking of, as that simply doesn't fit the definition.
The katana has one edge as you can see, there is no other edge to it, since the other side can't cut, puncture, slice etc meaning it's a single edged sword.
