What Is Ubu? 生ぶ — The Original, Unaltered Sword Tang
Ubu (生ぶ) describes a Japanese sword with an original, unaltered tang — an ubu-nakago (生ぶ茎) that has never been shortened or reworked since the smith finished it. On an ubu blade the tang keeps its original length, shape, file marks and peg hole, and if the smith signed it, the mei survives intact. Ubu is a mark of authenticity and originality, and it is one of the most desirable conditions a collector can find.
Because so many old blades were shortened (suriage) over the centuries, a genuinely ubu tang on an early sword is comparatively rare and prized. Reading whether a tang is ubu is a fundamental skill of nihonto appraisal.
What makes a tang ubu
An ubu-nakago retains all of the smith's original work at the tang end. The signs of an original tang are the opposite of the signs of suriage:
- Original nakago-jiri (茎尻) — the tang tip keeps its as-made shape (kurijiri, kengyo, ha-agari and so on) with even, consistent patina from tip to notches. No fresh re-shaping.
- Machi in their original position (区) — the hamachi and munemachi notches sit where the smith placed them; there is no machi-okuri (moved notches) betraying a shortening.
- A single, original mekugi-ana (目釘穴) — often just one peg hole, drilled by the smith, rather than the extra or relocated holes shortening produces.
- Continuous yasurime (鑢目) — the file marks run in one uninterrupted pattern along the whole tang, matching the smith's known style, with no change in direction or freshness.
- Full, correctly placed mei (銘) — if signed, the signature sits in its proper position and is complete, not running off the end or crowded by a later cut.
Why ubu is desirable
An ubu tang means the blade has survived in the form its maker intended. That carries real advantages:
- Original proportions — an ubu blade keeps its intended sugata (shape) and sori (curvature), so the design reads as the smith conceived it. A shortened blade's balance and elegance are compromised.
- Intact signature — an ubu signed blade preserves its mei, making attribution direct rather than dependent on kantei alone.
- Provenance and honesty — an original tang is harder to disguise and easier to authenticate; there is no reworking to hide.
For these reasons, all else equal, an ubu blade commands a premium over a comparable suriage or o-suriage one.
Ubu, suriage and the buyer's eye
Beware two traps. First, ubu is a condition, not a guarantee of a signature's truth — an ubu tang can still carry a gimei (false signature), so an original tang and an authentic mei are separate questions, both settled by kantei and NBTHK papers. Second, some later smiths' work is naturally ubu simply because it is younger and was never shortened; ubu is most meaningful and most valuable on early koto blades that escaped the widespread shortening of later eras.
When examining a tang, weigh the ubu evidence together: original tip, unmoved machi, single old peg hole, continuous file marks and even patina. The presence of all of them supports an ubu-nakago; any sign of machi-okuri, relocated holes or fresh work points instead to suriage.
Frequently asked questions
What does ubu mean for a Japanese sword?
Ubu (生ぶ) means the sword has an original, unaltered tang that has never been shortened or reworked since it was made. The tang keeps its original length, shape, file marks and peg hole, and any signature survives intact.
Is an ubu blade more valuable?
Generally yes. An ubu tang preserves the blade's original proportions and, if signed, its full mei, so all else equal an ubu blade commands a premium over a shortened (suriage or o-suriage) one, especially among early koto swords.
How do you tell if a tang is ubu?
Look for an original tang tip (nakago-jiri) with even patina, notches (machi) in their original position, usually a single original peg hole, and continuous file marks (yasurime) with no change in direction or freshness. Any moved notches or extra holes suggest suriage instead.
Can an ubu blade still have a fake signature?
Yes. Ubu describes the tang's condition, not the truth of the signature. An original tang can still carry a gimei, so authenticity of the mei must be confirmed separately through kantei and NBTHK papers.