Katana Abyssal Butterfly Hitatsura Hamon Kairyū Kagechō Koshirae 淵蝶

Hitatsura Hamon Full Tang Shinken (真剣) | Abyssal Butterfly Katana: TangGu (湯谷) Maru Blade (丸造) + TangGu (湯谷) Kairyū Kagechō Koshirae (海竜影蝶拵)

This katana is hand-forged (Tezukuri / 手作り) from high-carbon modern steel (高炭素現代鋼) in the Maru-zukuri (丸造) style. The blade is clay-tempered (yaki-ire / 焼入れ) to produce a Hitatsura hamon (full temper pattern / 満刃刃文) that spreads dynamically across the surface, symbolizing untamed elemental energy. The koshirae features a maru-gata tsuba (丸形鍔) forged from tetsu (鉄地, iron) with a blackened finish (煮黒) and a Kage Chō Sukashi (影蝶透) openwork design of shadowed butterflies, representing transformation and fleeting grace. The fuchi-kashira (縁頭) are made of hakudo (白銅), blackened (煮黒), and engraved with Kairyū (海竜) motifs. The menuki (目貫) are crafted from hakudo (白銅), blackened (煮黒), and shaped as Kenryū (剣龍) designs — dragons entwined with blades, symbolizing harmony between spirit and steel. The habaki (鎺) is a Suaka Habaki (素赤銅鎺) made from copper (素赤銅). The tsuka is wrapped in green tsuka-ito  over samegawa (鮫皮) with hishigami (菱紙) forming an even diamond pattern (菱組). The saya is finished in a green synthetic rayskin surface (緑色人造鮫皮塗), or upgraded to genuine rayskin upon request. The sageo (下緒) is rayon, available in any color, or upgraded to a Japanese-made sageo upon request.

TangGu (湯谷) Maru Blade

This blade is hand-forged (Tezukuri / 手作り) from high-carbon modern steel (高炭素現代鋼) in a monosteel construction called Maru-zukuri (丸造).

Blade Forging Details

• Blade Name: TangGu Traditionally Forged Maru Blade (丸造)
• Forging Method: This blade is hand-forged in the Maru-zukuri (丸造) construction from a single billet of modern high-carbon steel. Through precise clay-tempering (yaki-ire / 焼入れ), it achieves a distinctive Hitatsura hamon (full temper pattern) that spreads dynamically across the entire surface.
• Materials: Modern high-carbon steel (kōtanso gendai-kō / 高炭素現代鋼)
• Purpose: Suitable for Kenjutsu and Tameshigiri (test cutting) practice, collection, and display. Unsharpened blades are available for Iaido upon request.

Blade Specifications

• Blade Length (Nagasa刃長): Approx 71 cm
• Tang Length (Nakago 茎長): Approx. 25 cm
• Width at Base (Motohaba 元幅): Approx. 32 mm
• Thickness at Base (Motokasane 元重): Approx. 6 mm
• Width at Tip (Sakihaba 先幅): Approx. 24 mm
• Thickness at Tip (Sakikasane先重): Approx. 4 mm
• Kissaki Length (Tip 切先長): Approx. 35 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), Chū-kissaki (Medium-sized tip 中切先)
• Forging Pattern (Hada 鍛肌): None (Modern monosteel; no visible hada)
• Temper Line (Hamon 刃文): Clay-tempered Hitatsura (full temper) hamon — The blade is differentially hardened (yaki-ire / 焼入れ), creating a dramatic pattern.

Special Features and Workmanship

Hi (Groove) Engraving

• Type: Hi-Nashi (樋なし)
• Processing Range: None (No bohi) – Solid blade for added weight and strength

Polishing Work

• TangGu Polishing Levels:
  • High-grade shaping polish 上・成形研磨
  • High-grade rough polish 上・下研ぎ
  • High-grade final polish 上・仕上げ研磨

Fittings and Mountings

Blade Fittings

• Tsuba (Handguard 鍔): Maru-gata Tsuba (丸形鍔) – Forged from tetsu (鉄地, iron) and finished with a deep black patina (煮黒). The design features a Kage Chō Sukashi (影蝶透) openwork pattern of stylized butterflies.
• Fuchi-Kashira (縁頭): Made from hakudo (白銅, white copper), blackened (煮黒), and engraved with Kairyū (海竜, sea dragon) motifs.
• Menuki (目貫): Crafted from hakudo (白銅), blackened (煮黒), and shaped as Kenryū (剣龍, sword-dragon) figures.
• Habaki (鎺): Suaka Habaki (素赤鎺) – Made from plain copper (素赤銅).
• Samegawa (Ray Skin 柄鮫): Natural rayskin (鮫皮) beneath the tsuka-maki.
• Handle Wrapping (Tsuka-maki 柄巻): Green cotton (or rayon) tsuka-ito wrapped over hishigami (菱紙) in a diamond pattern (菱組).

Saya and Accessories

• Saya (Scabbard 鞘): Traditional-style saya (拵風鞘), reinforced with water buffalo horn (牛角) at the koiguchi (鞘口), kojiri (鐺), and kurigata (栗形) for added durability.
• Saya Lacquer (鞘塗): Green synthetic rayskin finish (緑色人造鮫皮塗), or upgraded to genuine rayskin upon request.
• Sageo (Cord 下緒): Japanese-made sageo available in multiple colors

Measurements

• Blade Weight: Approx. 0.65 kg
• Sword Weight (without Saya): Approx. 1.0 kg
• Total Weight: Approx. 1.3 kg
• Overall Length: Approx. 102 mm