A thread on 5ch shared a video of someone slowly test-cutting a paper carton with a Japanese sword (katana). While some viewers were struck by how the blade was worked in with small, repeated motions instead of one swift slash, others gave a cooler response — “anyone could do that,” “even a kitchen knife could manage it” — sparking debate over just how sharp the blade really was.
@
Not what I expected
Source: video.twimg.com / original post here
The pain hits you in slow motion, delayed lol
Only someone as sharp-eyed as me would even catch that
Seems doable once you get the knack for it lol
There's no way I could ever pull that off
I wonder if every samurai back in the day had the skill to bring that out
Well, that's true for paper anyway
Like clubbing them with something more like an iron rod
Just think about it for a second
Background and Key Points
Tameshigiri, the practice of test-cutting with a katana, has roots in Edo-period sword appraisal, when blades were tested on rolled tatami mats, bamboo, or even, historically, condemned criminals’ corpses, to certify a smith’s work and a swordsman’s technique. A rolled or soaked tatami mat is the modern standard because its fiber density is said to approximate human flesh resistance; a dry paper carton, by contrast, offers almost no resistance, which is exactly why the video split opinion. Katana blades are ground to an extremely acute, single-bevel edge (often under 15 degrees), very different from a Western kitchen knife’s more obtuse double bevel, so the “any knife could do this” comparisons posters made aren’t quite apples to apples, even if a sharp kitchen knife genuinely could slice an empty carton.
The thread’s real fault line wasn’t sharpness versus dullness, but interpretation of technique: some posters saw slow, deliberate pressure as proof of a bladeless-looking, unimpressive cut (“anyone could do that”), while others (37, 63) argued that cutting slowly, without toppling a light, unsecured, empty box, is actually the harder technical feat, since a fast slash would use momentum to stabilize the target while a slow draw relies purely on edge geometry and controlled force.
What the thread never engages with is that real historical sword combat, unlike choreographed test-cuts, involved armor, thrusting, and blunt trauma far more than clean slashes (briefly noted at 56-57), and that the dragonfly-splits-itself legend mentioned in the thread is folklore, not a documented phenomenon, even for legendary blades like Masamune’s.
*This article is excerpted and summarized from the 5ch (Hello! Project) thread “[Video] A Katana Test-Cut Slicing a Paper Carton in One Stroke Is Insanely Impressive!!!!!!!!!!!“.
