Konnichiwa Ukigumo-san!
Wow, You need a more advanced grade.
Yes, that's right. Some of the ancient schools have teachings that are different from modern schools.
Before starting a new story, let's recap the last one about "刃並" and "刃筋".
"刃筋" is the trajectory when swinging the sword, "刃並" is the trajectory of cut surface(or cut line).
But "刃筋" originally means refers to the vertical center line of the sword.
If the blade of the sword is not placed perpendicularly, it cannot cut anything. Therefore, when swinging a sword, "刃筋" must always be straight in the direction of the swing.
For this reason, "刃筋" which originally meant the central axis of the sword, came to mean the swing of the sword.
If "刃筋" is not aligned with the direction of the swing, the target will not cut. If you try to cut with the side of the sword "平地:Hiraji", the sword will bend or, worse, break.
Now onto the main topic.
However, some ancient schools have teachings that differ from those of modern schools. They teach you to cut along the "刃並" rather than the "刃筋". In this case, "刃並" should be at an angle of about 15 degrees from the "刃筋" in the direction of the swing. It's almost the same angle as "平地".
"Women in iaido" ai tempi del Coronavirus
If you cut on a "平地", the sword will bend or break. However, some ancient schools still teach cutting with this special angle of "刃並". Because you can cut a target clean off.
The "刃筋" and the "刃並" are different angles, but the target can be cut clean off. Why? Unfortunately, I don't know why either...
This is just my speculation, but I think it's probably a remnant of the time when people fought with swords. The ancient schools probably passed down this teaching as a technique for cutting the human body.
Of course, in modern times, we don't cut the human body with swords. And the ancient teachings were forgotten. And "刃並" measn "trajectory of the blade" which is the same as "刃筋" nowdays.
At least, I have never seen anyone wield a sword at a 15-degree angle.
YASKAWA BUSHIDO PROJECT / industrial robot vs sword master.
The number of inheritors of the ancient schools is decreasing. In particular, there are only a few people who handle genuine Japanese swords. The teachings of the ancient school are being forgotten, and in modern times robots wield swords.
NANGI