Tōshū

was a swordsmith who was supposedly forced by Ryūjin, a humanoid dragon, into forging the demon sword Dakki from his own scales.

History
He first appeared in manga Chapter 386, hiding from Ryūjin's murderous search for him. After Inuyasha's group chased the dragon away, Tōshū told them about how he met Ryūjin a year ago while traveling through the remains of a battlefield, and that Ryūjin demanded that Tōshū forge a sword for him using his dragon scales. To remind him of the deal, he gave Tōshū a mark on the right eye. Fearing for his own life, Tōshū attempted to forge Dakki, with many failed attempts. Inuyasha and his group protected and defended him when Ryūjin comes for the sword. While battling with Inuyasha, Ryūjin attempted to persuade Tōshū to give up the sword; Tōshū instead told Inuyasha about the dragon's weaknesses; namely, parts of his body were unprotected by scales, as he'd ripped them out to use in making powerful weapons. When Ryūjin was defeated, Tōshū quickly and ruthlessly plunged Dakki into the heavily-injured dragon, allowing it to consume Ryūjin's yōki and become a complete yōkai sword. It was then revealed that he intended to make the most powerful sword in the world, and that he was the one who offered to forge a sword for Ryūjin. Attempting to take Tessaiga's power, he attacked Inuyasha and managed to make a steadily widening crack in Tessaiga. His ambition proved to be his undoing, however, for his body deteriorated and fused with his sword. Finally, he met his demise when Dakki, afraid of breaking, instead let Tōshū's entire body take the damage, thus killing him.

Personality
Tōshū desired to have a strong blade of his own, eventually leading him to madness. He would stop at nothing to create a blade that was the strongest in the world to make him unbeatable. He was also an excellent actor, pretending to be a harmless and meek swordsmith to gain the trust of Inuyasha's group. It would seem that possessing Dakki slowly caused him to lose whatever sanity he had left.

Trivia

 * In the anime, Tōshū refers to energy or Yin as the key ingredient for making stronger blades. However, in the manga, he says hatred, malice, rage and other dark emotions are what create strong blades.
 * In the manga, when Dakki kills him, it leaves behind a mangled corpse because of his torso exploding. However, the anime has all but the hand that held Dakki vanish in dark smoke.

Toshu 刀秋