Japanese Knife Structure

  • Single vs. Double-Edge Knives: Where Craft Meets Function

    Every knife tells a story — of culture, craft, and cuisine. In this video, we explore the key difference between Japanese single-edge knives and Western double-edge knives, and how each design reflects a unique philosophy of cooking.

1. Single vs. Double-Edge Knives: Where Craftsmanship Meets Functionality

  • Across kitchens worldwide, two distinct knife philosophies have taken shape—the refined precision of Japanese single-edge blades and the practical versatility of Western double-edge knives. Their differences go beyond design; they reflect deep-rooted values about food, technique, and craftsmanship.


  • 1-1. Single-Edge Knives: Precision Born from Japanese Tradition

  • Japanese single-edge knives are celebrated for their elegance and exacting craftsmanship. As the name implies, only one side of the blade is sharpened, creating a uniquely refined geometry defined by the ridge line known as the Shinogi.

What Makes Single-Edge Knives Unique?

Unlike double-edge knives, single-edge blades are asymmetrical. The front (right) side is ground at a sharp angle, while the back has a subtle hollow—called Urasuki—that enhances cutting precision and allows food to separate smoothly from the blade.

Thanks to this design, the blade tapers to an extremely thin and sharp edge. During cutting, a small air pocket forms, helping ingredients glide off the knife with ease.

  • Advantages

    • Exceptional Sharpness
      Ultra-thin edge glides through ingredients with minimal resistance, producing clean cuts without crushing fibers—ideal for sashimi or delicate vegetables.
    • Simplified Sharpening
      Only one side needs sharpening, allowing for more consistent angles and easier maintenance.
    • Purpose-Driven Design
      Each knife has a clear role: Deba for fish butchering, Yanagiba for sashimi, Usuba for vegetables.

  • Disadvantages

    • Requires Skilled Technique
      The asymmetry means mastering straight cuts takes practice. A proper grip and awareness of the blade’s curve are essential.
    • Limited for Left-Handed Users
      Standard single-edge knives are made for right-handed users; left-handed versions must be custom-made or specially sourced.

  • 1-2. Double-Edge Knives: Western Practicality and Balance

  • Double-edge knives are sharpened symmetrically on both sides, creating a balanced structure that suits a wide range of cutting styles. Popular types like Santoku and Gyuto are staples in both Western and Japanese households today.

  • Advantages

    • Handles Hard Foods Well
      Even pressure on both sides provides stability for dense ingredients like pumpkin or potatoes.
    • Ambidextrous Use
      The symmetrical shape works equally well for right- and left-handed users.
    • All-Purpose Utility
      One knife can handle meat, fish, and vegetables—perfect for fast-paced, everyday cooking.

  • Disadvantages

    • Less Ideal for Thin Slices
      The dual-beveled edge makes it harder to achieve ultra-thin cuts like those required for sashimi.
    • Sharpening Takes Practice
      Maintaining symmetry when sharpening requires precise angle control on both sides—making it trickier for beginners.

  • 2. Cutting Philosophies of East and West: The Culture Behind the Blade

  • In every culture, the way we cut ingredients reflects more than technique—it reveals a philosophy of how we view food itself.

  • The Beauty of Pull-Cutting: A Japanese Approach

    In Japanese cuisine, freshness and the natural state of ingredients are paramount. A knife is not just a tool—it is a brush that reveals the inner beauty of food.
    Among the most revered techniques is hiki-giri (pull-cutting), performed with a Yanagiba knife. With one continuous stroke, the blade glides through delicate fish, preserving its fibers and leaving a mirror-like surface.

    This method is not only about efficiency—it is about respecting the ingredient’s integrity, presenting it as purely and beautifully as possible. In dishes like sashimi, the cut itself defines the dining experience.

  • Contrasting Ideals: Transformation in Western Cooking

    In Western cuisine, ingredients are equally valued, yet the philosophy often emphasizes transformation through cooking and sauces. A knife here is a multitool, preparing vegetables, meat, and herbs with efficiency before they are enhanced through heat, seasoning, and sauce.

    The double-edge blade, symmetrical and versatile, embodies this approach. Its practicality allows chefs to move swiftly and intuitively between tasks, supporting the creative interplay of flavor, texture, and sauce that defines much of Western cooking.

  • Choosing the Right Knife for the Moment

    Both traditions have their strengths, and the art lies in choosing the right knife for the right moment.

  • When Single-Edge Knives Shine:

    • Preparing sashimi or dishes where visual appeal is essential
    • Decorative vegetable cuts or precise garnishing
    • Filleting fish or tasks requiring technical finesse

  • When Double-Edge Knives Excel:

    • Everyday prep work across various ingredients
    • Quick, efficient slicing, chopping, and dicing
    • Cooking routines for all skill levels, from beginner to pro

  • A Cultural Heritage in Your Hands

    Japanese single-edge knives are more than sharpened steel—they are artworks of precision, shaped by centuries of tradition and master craftsmanship.
    Western double-edge knives represent innovation and adaptability, designed for efficiency in the modern kitchen.

    In today’s global culinary world, understanding both traditions allows us to cook with intention and artistry.
    Your choice of knife reflects your culinary philosophy—whether it leans toward preserving natural purity or transforming flavors through creativity. By embracing both, we carry forward the wisdom of East and West, one slice at a time.

3. Understanding Japanese Knife Craftsmanship: Craft, Structure, and Tradition

  • When it comes to Japanese knives, the differences go far beyond the edge.
    The choice of materials, the methods of forging, and the philosophy behind each blade reflect centuries of tradition.
    For anyone passionate about cooking, understanding these distinctions is key to appreciating the true artistry of Japanese knives.

3-1. Single-Edge Knives: Honyaki vs. Kasumi

  • Honyaki: Pure Steel, Pure Precision

    Forged from a single piece of high-carbon steel, Honyaki knives are the ultimate expression of Japanese forging, directly descended from samurai sword-making.
    They deliver exceptional hardness, the ability to hold a razor-thin edge, and an unmatched cutting experience.

    Yet this perfection comes with challenges. Their extreme hardness makes sharpening demanding, requiring proper whetstones and refined skill. They are also more brittle, demanding careful handling. And because the forging process is so intricate, results vary greatly depending on the craftsman’s mastery.

  • Kasumi (Awase): Practical Harmony

    In contrast, Kasumi knives are made by laminating a hard steel core with softer iron, creating a harmonious balance between sharpness and usability. They are easier to sharpen and more forgiving in daily use, making them suitable for professionals and dedicated home cooks alike.

    The trade-off: the bond between dissimilar metals can sometimes cause warping, and the long-term performance depends heavily on the quality of the forge. Still, a well-crafted Kasumi knife beautifully combines tradition and accessibility.

3-2. Double-Edge Knives: Zenkou vs. Kasumi Hari Awase

  • Zenkou (All Steel): Durable and Consistent

    Forged from a single piece of steel, Zenkou knives are valued for their strength, edge retention, and uniform performance. Because the blade is hardened throughout, they resist chipping and maintain sharpness over long use—making them a trusted choice for professionals who demand reliability.

    However, this same uniform hardness means sharpening takes more time and effort compared to laminated knives. Without the softer layers found in Kasumi construction, the whetstone must grind only hard steel, requiring patience and skill. Structurally, it would be possible to re-shape a Zenkou knife into a single-bevel edge, but in practice this is uncommon and not generally recommended, as these knives are designed for double-edge balance.

  • Kasumi Hari Awase: Layered Craftsmanship

    Kasumi knives feature a hard steel core laminated with softer outer layers. This creates a balance of sharpness, shock absorption, and ease of sharpening. The softer layers make maintenance smoother, allowing even dedicated home cooks to restore an edge with less effort.

    The trade-off is that the outer layers can deform slightly under heavy use, and edge retention is typically shorter compared to Zenkou knives. In addition, as double-bevel designs, they cannot replicate the specialized precision of traditional single-bevel Japanese knives.

  • A Shared Legacy

    Both Zenkou and Kasumi Hari Awase represent different answers to the same challenge: how to combine sharpness, durability, and usability. Whether you choose the resilience of all-steel construction or the practicality of laminated layers, each blade reflects centuries of Japanese craftsmanship and the cultural values behind cooking itself.

FAQ About Single-Edged and Double-Edged Knives

Knife_forging_process

Q1. What is the difference between single-edged and double-edged knives?

Single-edged knives are sharpened on only one side, with the reverse side either flat or slightly concave. This traditional Japanese design enables unmatched precision and produces smooth, clean cuts. Double-edged knives, by contrast, are sharpened symmetrically on both sides. This Western-style geometry offers greater versatility, making them suitable for a wide variety of ingredients and cooking styles.

Q2. Why did single-edged knives evolve in Japan?

The evolution of single-edged knives reflects Japan’s emphasis on delicacy and precision in cuisine. They were especially refined for preparing fish, where flawless cuts preserve texture, umami, and visual appeal. Japan’s heritage of sword-making also played a role in the craftsmanship and geometry of these blades.

Q3. Which type is recommended for beginners?

Double-edged knives are generally more beginner-friendly. Their symmetrical edge makes them easier to sharpen, more intuitive to use, and suitable for a wide range of cuisines. They also work equally well for left- and right-handed users and are often more affordable than handcrafted single-edged knives.

Q4. Are cutting techniques different between single-edged and double-edged knives?

Yes. Single-edged knives emphasize pull-cutting (hiki-giri), using smooth, controlled strokes that minimize damage to delicate fibers. Double-edged knives accommodate a wider range of techniques, including push-cutting and rocking motions, which suit diverse ingredients and Western-style preparations.

Q5. Can left-handed people use single-edged knives?


Not without modification. Standard single-edged knives are designed for right-handed users. For left-handed chefs, special versions with reversed blade geometry are required to ensure the same precision and control.

Q6. Which type is preferred by professional chefs?

It depends on the cuisine. In traditional Japanese kitchens, single-edged knives remain essential for precision tasks like sashimi and kaiseki preparation. In Western or fusion kitchens, double-edged knives are favored for their versatility and speed. Many chefs own both, choosing the right knife for the right context.

Ⅰ. Why Are Japanese Knives Single-Edged?

  • In Japan, a blade has never been just a tool.
    It embodies history, pride, and the pursuit of perfection.
    And nowhere is that legacy more visible than in the design of Japanese single-edged knives.

    Why are they made this way?
    The answer is rooted not in technique alone, but in centuries of tradition, peace, and craftsmanship.

  • (1) Blades Were Never Just for Battle

    In Japan, blades have always been more than weapons.
    They were seen as symbols of pride, beauty, and technical mastery.

    One key figure in this story is Emperor Go-Toba, born in 1180 during Japan's Kamakura period.
    He became emperor at just three years old and later ruled as a cloistered emperor.

    But Go-Toba was no ordinary ruler—he had a deep passion for blades.
    He supported swordsmiths across Japan and even participated in forging swords himself.

    This deep cultural respect for blades became part of Japanese identity—and eventually shaped the knives used in Japanese kitchens today.

  • Edo

    (2) Peace Perfected the Blade

    During the Edo period, Japan experienced more than 260 years of peace.
    With no wars to fight, swordsmiths turned their attention from weapons to tools for daily life—most importantly, kitchen knives.

    At the same time, chefs elevated cooking into an art form of refinement and presentation.
    This peaceful environment nurtured the cultural values that demanded precision and beauty in food preparation.

    It was in this context that the single-edged knife evolved, perfectly suited to the needs of Japanese cuisine.

  • (3) The Turning Point — From Swords to Knives

    In 1876, the Haitōrei edict banned the carrying of swords in public.
    Many swordsmiths lost their livelihoods—but not their skills.

    They redirected their craftsmanship to kitchen knives, transforming towns like Sakai and Seki into global centers of blade-making.
    The techniques once used for samurai swords now lived on—in knives for the Japanese table.

  • Why Single-Edged?

    The reason lies in history: a long era of peace, a culture that elevated food into art, and craftsmen who adapted their skills from swords to cuisine.
    The result is a blade that offers unmatched beauty and precision.

    A single-edged knife allows chefs to:

    • Separate fish from bone with flawless accuracy
    • Slice along natural fibers without crushing the texture
    • Preserve flavor and presentation, keeping dishes pure and elegant


    In Japan—where food is treated as an expression of culture and aesthetics—the single-edged knife was not simply practical.
    It became essential.

  • A Knife That Reflects a Nation

    A Japanese knife is far more than a kitchen tool.
    It is a product of history, peace, craftsmanship, and cultural pride.

    Every cut tells a story—of emperors and swordsmiths, peaceful centuries, and the pursuit of perfection.
    The single-edged blade is more than a technical choice.
    It is a reflection of Japan’s cultural soul.
All Japanese Knives from Sakai

Ⅱ. Is Your Knife a "Versatile Partner" or a "Specialized Craftsman"?

  • Pick up the knife in your kitchen.
    Is it a reliable all-rounder, ready to tackle almost anything? Or is it a specialized expert, crafted for a single, perfect purpose?

    This question reveals the fundamental difference between Japanese and Western knives.

  • Japanese Knives: The Craftsman’s World of Perfection

    Heritage of the Sword
    Japanese knives evolved from samurai sword-making, designed primarily for fish and vegetable preparation.
    In Japanese cuisine, beauty matters—not crushing cells, preserving texture, and creating elegant cross-sections.

  • Key Characteristics

    • Single-edged structure: Achieves flawless separation and smooth cuts
    • Purpose-driven design: Each knife has one clear role—Yanagiba for sashimi, Deba for fish, Usuba for vegetables
    • Ultimate sharpness: Razor-thin edge that enhances both taste and presentation
    • Insert-style handle: Designed for longevity—handles can be replaced when worn

  • The Aesthetic of Sharpening
    In Japan, knives are treasured like swords.
    Owners sharpen them regularly, often keeping a single knife for decades. This is more than maintenance—it reflects a uniquely Japanese aesthetic of care and continuity.

  • Japanese Cuisine Philosophy: Respect for Ingredients

    • Cooking as art, where beauty and flavor are inseparable
    • Ingredients are the protagonist, especially in sashimi
    • Technique is delicate, aiming never to damage the ingredient

  • Western Knives: Practicality and Efficiency

    Born from Meat-Centric Culture
    Western knives developed in societies where meat was central. Cutting through bones, breaking down large cuts, and preparing hearty stews required tools that were robust and versatile.

  • Key Characteristics

    • Double-edged structure: Symmetrical, intuitive for both right- and left-handed users
    • Multi-purpose design: One knife—like the Gyuto or Petty—can handle meat, fish, and vegetables
    • Durable build: Strong enough to cut through bone-in meat
    • Riveted handle: Sturdy, permanent construction

  • Practicality First
    Western knife culture emphasized efficiency. When a knife dulled, the rational choice was often replacement rather than resharpening. This wasn’t neglect—it was a time-saving decision aligned with the pace of life.

  • Western Cuisine Philosophy: Efficiency in Nourishment

    • Cooking as a means, creating meals quickly and practically
    • Flavor completed with seasonings and sauces
    • Emphasis on powerful preparation, especially with meat

  • Two Philosophies, One Kitchen

    The contrast is not simply about knives—it reflects two different relationships with food.

    • Japanese knives: The crystallization of a thousand years of craftsmanship and aesthetic sense, treating cooking as art
    • Western knives: The embodiment of efficiency and universality, a partner adapted to modern life


    Today, the line is blurred. The Santoku, now Japan’s most common household knife, is itself a fusion—born from the Western Gyuto but adapted with Japanese sensibility.
    There are also double-edged Japanese knives (like Nakiri) and Japanese-made Western knives, showing that traditions continue to evolve and intermingle.

  • What’s Your Style?

    When you hold a Japanese knife, you're gripping the "crystallization of a thousand years of craftsmanship and aesthetic sense". It's an artwork that embodies respect for ingredients and the aspiration for the perfect cut.

    When you hold a Western knife, you're gripping an "efficient and practical universal tool". It's a reliable partner perfectly adapted to modern lifestyles.

  • What's Your Cooking Style?

    • If you pursue ingredient beauty and ultimate sharpness → Japanese knives
    • If you value time-saving versatility → Western knives
    • If you want the best of both worlds → Japanese-made Western knives

    In the next section, we’ll dive deeper into blade structure—because the difference between single-edge and double-edge isn’t just a matter of shape.
    It’s the difference between two philosophies of cooking itself.

Ⅲ. The Mystical Technology of Japanese Knives:

  • Three Precision Structures That Captivate Chefs Worldwide

    Japanese knives are treasured by top chefs around the world. Behind their breathtaking sharpness lies a set of ingenious design secrets, refined over centuries by master craftsmen. These wa-bocho are more than cooking tools—they are artworks born from cultural philosophy, carrying the spirit of Japanese cuisine.

    So, what makes them so extraordinary?

  • The Three Precision Structures of Japanese Knives

    The phenomenal performance of single-edged Japanese knives is built on three innovations: tapering, angle variation (twist), and urasuki (back hollowing).
    Each alone is remarkable—but together, they create a harmonious system of science and art, enabling a cutting performance unmatched by any other knife.

  • (1) Tapering: Mastering Friction Through Subtle Thickness Changes

  • Japanese blades gradually thin from heel to tip, a structure called tapering. This creates microscopic gaps between the blade and the food, dramatically reducing friction.

    • Smooth Cutting Sensation: Push or pull cuts glide effortlessly
    • Food Integrity: Fibers remain intact, texture is preserved
    • Freshness Protection: Less friction means less heat, keeping ingredients vibrant

    Crafting the perfect taper requires sensitive judgment by skilled smiths. Too thin compromises durability, too thick reduces sharpness. Achieving this balance is one of the hallmarks of Japanese craftsmanship.

  • (2) Angle Variation (Twist): Precision by Design

    Japanese knives are designed with subtle angle changes along the edge. This “twist” ensures the blade performs at its best for its intended purpose.

  • Examples:

    • Yanagiba: Heel 13° → Tip 11° → flawless sashimi slices
    • Usuba: Heel 10° → Tip 8° → delicate vegetable cutting

    Maintaining these variations requires proper sharpening techniques. Without skilled sharpening, the blade loses the very precision that defines its performance.

  • (3) Urasuki: The Signature of Japanese Knives

  • Perhaps the most distinctive feature, urasuki is the concave hollowing on the back of the blade. This reduces the contact surface with food, enabling extraordinary sharpness.

    • Minimal Friction: Only a small area touches the food
    • Flavor Protection: Especially vital for sashimi, preserving umami
    • Point Contact Cutting: Creates the ideal state where the blade glides with pinpoint precision


    Crafting urasuki requires exceptional skill and experience. Too wide weakens the blade, too narrow reduces effectiveness. It is a technique handed down only to the most skilled artisans.

  • Why These Technologies Emerged: Deep Roots in Japanese Culinary Culture

    • Respect for Ingredients: In Japanese cuisine, the beauty of the cut itself becomes flavor.
    • The Aesthetics of "Ma" (Negative Space): The microscopic space between blade and ingredient, the rhythm of angle shifts, and the point contact of urasuki embody Japan’s cultural pursuit of harmony.
    • Seasonal Adaptation: From spring bamboo shoots to winter fugu, diverse seasonal ingredients required knives optimized for each food.
    • Craftsmanship Heritage: Generations of masters refining skills created today’s sophisticated knives.

  • Universal Appeal Beyond Japan

    Today, chefs in French, Italian, and global cuisines are captivated by Japanese knives. Their precision, sharpness, and respect for ingredients are values shared by chefs worldwide.

    Japanese knives are not just tools—they are bridges connecting culinary traditions across borders.

    When you hold one, you hold centuries of refinement, cultural pride, and a relentless pursuit of perfection.

    The three precision structures—tapering, twist, and urasuki—are not merely technical achievements. They are the crystallization of a philosophy where craftsmanship and cuisine merge into art.

Ⅳ. The Difference Between Honyaki and Zenkou (All Steel) Knives

  • Japanese knives made from a single piece of steel fall into two categories: Honyaki and Zenkou (All Steel). Understanding the difference between the two is essential when choosing the right knife.

  • Honyaki: Forged to Perfection

    Honyaki knives are created through forging, a meticulous process rooted in the tradition of Japanese sword-making. The steel is repeatedly heated, hammered, and shaped by hand. This not only aligns and compresses the internal crystal structure of the metal but also gives the blade:

    • Exceptional durability and toughness, able to withstand impact and stress
    • Superior hardness and long-lasting sharpness, requiring less frequent sharpening
    • Effortless cutting performance, even with thin blades slicing smoothly through food


    More than just tools, Honyaki knives are works of art, infused with the passion and skill of the craftsman. The smooth glide through ingredients, the precision of each cut, and the blade’s enduring sharpness create a truly elevated culinary experience. For chefs and enthusiasts alike, a Honyaki knife represents the highest expression of Japanese craftsmanship.

  • Zenkou (All Steel): Practical and Accessible

    In contrast, Zenkou (All Steel) knives are made by shaping a single piece of steel with a mold, without the forging process. Because the steel’s internal structure is not refined through hammering, these knives:

    • Have lower toughness and durability compared to Honyaki
    • Are more affordable and well-suited for everyday use
    • Offer reasonable performance without the same artistry or refinement

    For those seeking practicality and value, Zenkou knives are a reliable option.

  • Choosing Between the Two

    • Honyaki: For professionals and serious enthusiasts who value artistry, tradition, and superior cutting performance
    • Zenkou: For those who prioritize affordability and functionality in daily cooking

  • Honyaki knives stand as a pinnacle of Japanese craftsmanship, while Zenkou knives provide practical accessibility. Both have their place, but their differences highlight the spectrum of Japanese knife-making—from practical utility to timeless artistry.