Tessaiga (鉄砕牙, also known as Tetsusaiga) is a fictional sword in the anime and manga series InuYasha, wielded by half-human, half-yōkai (hanyō) InuYasha. The kanji, directly translated, means "iron-crushing fang". [1]

In the English adaptations of InuYasha, Tessaiga is called Tetsusaiga (or Tetsaiga) due to an error in translation in the early days of the manga when the tiny っ (tsu) kana (which indicates a glottal stop, or a doubling of the consonant that follows it) was misread as a full-sized つ (tsu) kana, altering the romanization and pronunciation of the word. Both Tetsusaiga and Tessaiga can come from the kanji; the proper spelling depends on how the name is pronounced. The proper romanization is Tessaiga. By the time Viz, the company that translates the anime and manga, had realized the error it was too late.

The Tessaiga was made from a fang of InuYasha's and Sesshomaru's full-fledged demon father. In its 'docile' form, the sword looks like a regular (and rather battered) katana. When wielded properly, it transforms into a weapon roughly the size of a car bumper that somewhat resembles a falchion, and has the power to slay 100 demons in one swing by striking the Wind Scar.

However, in a confrontation with Goshinki, a detachment from Naraku, the Tessaiga was broken in half. The sword's creator Totosai was able to repair the Tessaiga, but in doing so he used one of InuYasha's fangs. The result is that Tessaiga now became dependent on the strength of InuYasha himself - making the weapon heavier and more difficult for InuYasha to wield. After much training, InuYasha learns how to use a greater power created from the convergence of multiple Wind Scar attacks (Kaze no Kizu) from a powerful opponent, that is known as Backlash Wave. It was sought after by Sesshomaru because he is jealous that InuYasha received the more powerful weapon from their father, until he found out that he can't wield the sword. Somehow its sheath can 'summon' the sword, and the Tessaiga itself has great magical power - it can act of its own accord even when InuYasha has fallen unconscious.

Tessaiga also binds the powerful demon blood that came from InuYasha's father which can transform him into a full demon, and it can absorb magical abilities from the blood of a creature that possesses them, for example, barrier shattering (from Shiori 's barrier orb) and Kongōsōha (diamond spear attack, from Hosenki (Hōsenki).

In the third movie of the InuYasha franchise, the combined powers of the Tessaiga and the Tenseiga succeeded in defeating the oppose Songa (Sō'nga), the sword of world conquest, which was stronger than either of them alone.

Special attacks

• Anti-demon barrier: InuYasha and Sesshomaru's father put a protective barrier within the sword, so that pure demons will be repelled. InuYasha, being a half-human half-demon, can wield the sword fine. As a powerful demon, Sesshomaru can wield the sword for a short period of time. Humans can wield the Tessaiga in its untransformed (katana, Japanese for sword) state.
• Wind Scar (Kaze no Kizu, 風の傷): Special attack that kills 100 demons with one strike.
• Backlash Wave (Bakuryūha, 爆流破): Tessaiga's ougi (or ultimate technique). Uses the opponent's strong demonic forces and unleashing the Wind Scar at the right point, the demon's energy will be reflected back with the added power of the Wind Scar. Power is amplified many folds.
• Barrier Shattering: Gained from Shiori's orb for saving her from her grandfather and his bat yōkai, this technique completely shatters barriers (including Naraku's for a while). When used, Tessaiga glows red. Only the strongest barriers cannot be shattered by this attack.
• Diamond Spear (Kongōsōha, 金剛槍破): Attack gained from Hōsenki after Naraku had used a shard of the jewel to corrupt him and caused him to attack InuYasha. The diamond shards are able to pierce Naraku's stronger barriers.
• Dragon Scale Tessaiga: Having defeated Dakki, Tessaiga gains the ability to absorb yōkai. This technique becomes especially useful against yōkai's possession skills.
• Sheath of Tessaiga (Tessaiga no Saya): Can deflect or resist demonic energy attacks with the barrier used to contain Tessaiga's power. However it can only withstand a limited number of attacks.