Katana Silent Star Kobuse Blade Yusei Koshirae 玄圃草

Clay Tempered Full Tang Shinken (真剣) | Silent Star Katana: TangGu (湯谷) Kobuse Blade (甲伏造) + TangGu (湯谷) Yusei Koshirae (幽星拵)

The uchigatana-style koshirae (打刀拵) combines traditional design with functional strength. The blade is forged in Kobuse-zukuri (甲伏造) construction, with a hardened outer steel layer and softer core, a method used in tamahagane blades for balanced cutting power and shock absorption. The surface shows Mokume-hada (杢目肌), a wood-grain pattern created by folding and forging. Along the edge runs an irregular midare hamon（乱れ刃文）with gunome elements, formed through clay tempering (覆土焼入れ). The saya (鞘) is finished in black raden-style lacquer (螺鈿塗) with subtle reflective particles. Kojiri is metal reinforced; koiguchi and kurigata are buffalo horn. A black silk sageo (下緒) is tightly woven. The tsuka (柄) is wrapped in black cotton ito over aged yellow samegawa (鮫皮), reinforced with hishigami (菱紙). Brass menuki shaped as leaf blades. Fuchi and kashira (縁頭) are steel with karakusa (唐草) patterns. The tsuba (鍔) is a mokko-gata (木瓜形) iron guard with blackened patina (煮黒仕上げ) and plum blossom sukashi (梅花透かし).

TangGu (湯谷) Kobuse Blade

This blade is hand-forged (Tezukuri / 手作り) from our own refined steel in Kobuse-zukuri (甲伏造) construction. This method reflects the structure of traditional Tamahagane (玉钢) swords, balancing edge hardness and core flexibility for resilience and cutting performance.

Blade Forging Details

• Blade Name: TangGu Traditionally Forged Kobuse Blade (甲伏造)
  

• Forging Method: This blade is forged in Kobuse-zukuri（甲伏造）style, with a hardened outer layer over a softer iron core. It is differentially hardened using clay tempering（覆土焼入れ）, producing a sharp edge, resilient spine, and a visible hamon（刃文).

• Materials: Steel refined in-house using traditional methods（伝統的手法による自家製鋼材）

• Purpose: Designed for Iaido (non-sharpened), Kenjutsu, and Tameshigiri (test cutting) practice, as well as for collection, display, and appreciation by enthusiasts and connoisseurs.

Blade Specifications

• Blade Length (Nagasa刃長): Approx 73 cm
• Tang Length (Nakago 茎長): Approx. 24 cm
• Width at Base (Motohaba 元幅): Approx. 31 mm
• Thickness at Base (Motokasane 元重): Approx. 6 mm
• Width at Tip (Sakihaba 先幅): Approx. 22 mm
• Thickness at Tip (Sakikasane先重): Approx. 4 mm
• Kissaki Length (Tip 切先長): Approx. 40 mm
• Mekugi-ana (Peg Hole 目釘穴): 1

Blade Characteristics

• Shape: Shinogi-zukuri (ridged blade 鎬造), Iori-mune (flat ridged spine 庵棟), Ō-kissaki (Large tip 大切先)

• Forging Pattern (Hada 鍛肌): Mokume-hada（杢目肌）— wood-grain pattern with swirling, ring-like textures from folding and layering.
• Hamono (Blade Pattern 刃文): Irregular Midare with Gunome influence（互の目交じりの乱れ刃文）— uneven waves and rounded peaks formed by clay tempering.

Special Features and Workmanship

Hi (Groove) Engraving

• Type: Marudome-Hi (丸止樋), deeply engraved
• Processing Range: Extends to the tip, fully polished inside the groove

Polishing Work

• TangGu Polishing Levels:
  • Highest-grade shaping polish 最上・成形研磨 
  • Superior rough polish 最上・下研ぎ 
  • Detailed final polish 最上・仕上げ研ぎ 
• Key Features:

  • The blade has refined geometry and balanced handling, made with Kobuse (甲伏) construction — a hard outer steel shell around a softer core for cutting strength and resilience. Traditional polishing reveals a Hamon (刃文) with Midare and Gunome elements, Mokume-hada (杢目肌) grain, and a defined ridge line (Hōmi / 峰).

Fittings and Mountings

Blade Fittings

• Tsuba (Handguard 鍔): Mokko-gata（木瓜鍔）iron tsuba with blackened patina (煮黒仕上げ), featuring plum blossom-shaped sukashi cutouts.
• Fuchi-Kashira (縁頭): Brass with engraved karakusa（唐草）motifs.
• Menuki (目貫): Brass menuki shaped like leaf blades.
• Habaki (鎺): Hand-forged brass with aged finish.
• Samegawa (Ray Skin 柄鮫): Genuine ray skin aged to a soft yellow hue.
• Handle Wrapping (Tsuka-maki 柄巻): Black cotton ito, tightly wrapped in traditional style.

Saya and Accessories

• Saya (Scabbard 鞘): Katana-style (打刀拵) scabbard with buffalo horn koiguchi and kurigata. Kojiri reinforced with metal for durability.
• Saya Lacquer (鞘塗): Raden-style lacquer (螺鈿塗), glossy black surface with subtle reflective particles.
• Sageo (Cord 下緒): Black silk sageo, tightly woven.

Measurements

• Blade Weight: Approx. 0.65 kg
• Sword Weight (without Saya): Approx. 1.0 kg
• Total Weight: Approx. 1.3 kg
• Overall Length: Approx. 100 mm