The katana's edge is ground to 15 degrees and folded through 16 layers of tamahagane steel, a forging method unchanged since the Kamakura period. What began as battlefield necessity in 1185 evolved into a craft so disciplined that a single blade required three months of differential tempering, clay application, and water quenching timed to the rhythm of hammer and anvil. By the Edo era, when samurai transitioned from warrior to administrator, the sword became symbol rather than tool, and the forging tradition contracted into a lineage of fewer than 300 certified smiths nationwide. Today, samurai sword making class Tokyo programs preserve that lineage not as museum exhibit but as participatory craft. The Samurai Museum Shinjuku anchors its collection—armor, tanto daggers, tachi blades spanning four centuries—with hands-on workshops where tamahagane, the high-carbon steel smelted in traditional tatara furnaces, is shaped under guidance. You work the same coke-fired forge, the same water trough, the same grinding stones that defined Japanese bladesmithing for 800 years. The katana's curve, its hamon temper line, the yokote ridge separating blade from tip—all emerge not from explanation but from repetition, the way apprentices learned before written manuals existed. Katana workshops in Tokyo cluster in Shinjuku and Asakusa, where English-speaking instructors translate not just vocabulary but the spatial grammar of the forge: how slack in the wrist softens the hammer blow, how quench speed determines hardness, how the blade's spine remains flexible while the edge holds sharpness. The museum context matters. Displays of Muromachi-era armor and Heian-period scrolls situate the workshop within a material continuum, so the tsuba hand guard you examine in a vitrine connects directly to the nakago tang you file during the session. This is not performance; it is transmission, compressed into two hours rather than two decades. The forge experience does not produce a finished katana—tempering alone requires days—but it does yield a functional tanto or wakizashi short blade, edge-ground and wrapped, that clears Japanese customs as craft object rather than weapon. The distinction matters legally and symbolically. What leaves the workshop is proof of technique, a 30-centimeter length of folded steel that holds its geometry because you learned to read the color of hot metal, to time the quench, to respect the interval between hammer strokes. That knowledge, more than the blade itself, is what the tradition protects.