The Unagisaki: Japan's Specialized Eel-Slaying Blade
The unagisaki is one of Japan's most fascinating and specialized kitchen knives, purpose-built for a single, remarkably specific task: preparing unagi, or freshwater eel. While most Western cooks might reach for a general-purpose knife to tackle any ingredient, Japanese culinary tradition has produced dozens of blade styles, each optimized for particular ingredients or techniques. The unagisaki stands out even among these specialists as a knife so dedicated to its purpose that it varies in design depending on which region of Japan you're in.
Understanding the Unagisaki's Purpose
Preparing eel is a task that demands both precision and speed. Freshwater eel has slippery, tough skin and a sinuous body that writhes even after death, making it notoriously difficult to handle. The unagisaki's design addresses these challenges head-on. The knife must pierce the eel's head to pin it to the cutting board, slit along its body without damaging the delicate flesh, and remove the backbone in one clean motion—all while the eel is doing its best to escape.
The blade is single-beveled (sharpened on only one side), typically ranging from 15 to 30 centimeters in length, with a pointed tip essential for the initial pinning motion. What makes the unagisaki particularly interesting is its regional variation: Tokyo-style unagisaki knives are shorter and designed for splitting eels from the back, while Osaka-style versions are longer and split from the belly. This difference stems from historical class distinctions—Osaka merchants preferred not to reference "seppuku" (ritual belly-cutting) in their food preparation, while Tokyo's samurai class had no such qualms.
Steel Types and Construction
Traditional unagisaki knives are forged from high-carbon steel, with several varieties commonly used:
White Steel (Shirogami): This is pure, simple carbon steel prized for its ability to take an exceptionally sharp edge. White steel is relatively easy to sharpen but requires diligent maintenance to prevent rust. White #1 and White #2 are common grades, with #1 being harder and holding an edge longer.
Blue Steel (Aogami): This steel contains trace amounts of chromium and tungsten, making it slightly more wear-resistant than white steel while maintaining excellent edge retention. Blue steel is harder to sharpen but stays sharp longer during the repetitive work of eel preparation.
Damascus-patterned Unagisaki: Modern unagisaki knives often feature Damascus-style layered steel construction, with a hard carbon steel core wrapped in multiple layers of softer steel. This creates the distinctive wavy pattern on the blade while providing the benefits of both hard and soft steel—edge retention from the core and flexibility from the outer layers. These knives typically feature 33, 67, or even 100+ layers.
The handle is traditionally made from magnolia wood (hō-no-ki), which is lightweight, water-resistant, and comfortable during extended use. The wood naturally develops a patina over time that actually improves grip.
Restoration and Maintenance
Maintaining an unagisaki requires dedication, but the process connects you to centuries of Japanese culinary tradition.
Daily Maintenance:
After each use, immediately wash the knife with warm water and mild soap, using your hands rather than a sponge to avoid scratching the blade. Dry it thoroughly with a soft cloth—carbon steel will rust if left wet. Some professionals wipe their blades with a thin coat of food-grade camellia oil after drying to prevent oxidation.
Sharpening:
The single-bevel edge requires a different sharpening technique than Western knives. You'll need Japanese water stones, typically starting with a 1000-grit stone for regular maintenance, moving to 3000-6000 grit for polishing.
Hold the knife at a 15-20 degree angle on the beveled side and sharpen using smooth, consistent strokes from heel to tip. The flat (ura) side requires only light pressure to remove any burr and maintain its slight concavity. This concavity, called "urasuki," actually makes the knife cut more cleanly by reducing friction.
Restoration of Neglected Blades:
If you've inherited or purchased a rusty unagisaki, restoration is possible:
- Remove rust using a rust eraser (a specialized rubber block) or fine-grit sandpaper (600-1000 grit), working with the grain of the steel
- For Damascus blades, be gentle to preserve the pattern
- Once clean, start sharpening with a 400-800 grit stone to re-establish the edge
- Progress through finer stones (1000, 3000, 6000 grit) to polish
- Consider having a professional handle major repairs like chips or improper bevels
Storage:
Store your unagisaki in a dry place, ideally in a protective sheath (saya) made from magnolia wood. Never store it wet or in a leather sheath, which can trap moisture. Some professionals store their knives with a light coating of camellia oil and rice paper between uses.
The Lighter Side of Eel Knives
Here's something amusing: the unagisaki has inspired a peculiarly Japanese form of performance art. In major Japanese cities, particularly Tokyo's Tsukiji Outer Market and specialty restaurants, veteran eel chefs sometimes demonstrate their skills in a practice called "unagi no ikizukuri" (live eel preparation). Tourists gather to watch these masters pin and fillet a squirming eel in under 30 seconds—a process that looks more like wrestling than cooking.
The knife work is so rapid and precise that spectators often can't follow what's happening. One moment there's an angry, writhing eel; the next moment it's been transformed into perfectly butterflied fillets ready for grilling. The eel, for its part, seems as surprised as the audience.
There's also the story of unagisaki knives in competitive cooking shows. On several Japanese cooking programs, contestants unfamiliar with traditional tools have been challenged to prepare eel using an unagisaki. The results are predictably chaotic—imagine trying to use a specialized surgeon's scalpel when you've only ever used a kitchen knife. Eels escape onto the floor, chefs accidentally pin their own sleeves to cutting boards, and in one memorable incident, a contestant was so intimidated by the thrashing eel that he simply stood frozen, knife raised, for nearly a minute before attempting to proceed.
Perhaps most humorously, the unagisaki has become an unexpected symbol in Japanese pop culture for "over-specialization." There's a running joke in Japanese comedy sketches about the absurdity of having a knife for literally everything—"What's next, a knife specifically for Tuesday carrots?" The unagisaki, being so absolutely dedicated to a single creature, often features in these routines as the ultimate example of this tendency.
Conclusion
The unagisaki represents everything beautiful about Japanese knife-making tradition: dedicated craftsmanship, specialized purpose, and the belief that doing one thing exceptionally well is better than doing many things adequately. While most home cooks will never need to prepare fresh eel, understanding tools like the unagisaki deepens our appreciation for the care and precision embedded in Japanese culinary culture.
For those who do work with eel, or collectors who appreciate specialized tools, a well-maintained unagisaki is a lifetime investment. Treat it with respect, keep it sharp and rust-free, and it will serve faithfully through thousands of eels—even if they don't always cooperate.
