(In the original story, Goshinki's teeth were precisely the crucial material used to forge the demon sword Tōkijin.
That was because, in another timeline, Goshinki had also bitten through Tessaiga.
However, what he bit through was not Tessaiga in its rusty-blade form, but the imposing demon sword Tessaiga that Inuyasha wielded in his half-demon form.
At the time, Goshinki had used mind reading to anticipate Inuyasha's thoughts and every movement.
After Inuyasha swung his sword, Goshinki passed through the Wind Scar and bit down on Tessaiga's blade with extraordinary precision.
With a single bite, Tessaiga snapped in two.
This triggered the awakening of the demon blood within Inuyasha for the first time.
Goshinki was then killed by the fully transformed Inuyasha, dying filled with bitter resentment.
Sesshomaru caught the scent of his younger brother's blood on the wind and realized it no longer carried a half-demon's aura, but a full demon's. Thus, he came to the scene. Naturally, he then discovered Goshinki's head and other remains, and smelled Tessaiga's scent on Goshinki's teeth, allowing him to determine that the sword had been bitten through by those demon fangs.
Afterward, Sesshomaru took Goshinki's head to the swordsmith Kaijinbo, who used Goshinki's revived teeth to forge a superb sword.
Namely, Tōkijin.
Without a master, Tōkijin possessed an extremely powerful evil aura and could control its wielder.
Miroku, Totosai, and the others could not even approach it, let alone pick up this sinister sword.
Inuyasha swung his reforged Tessaiga in an attempt to destroy it, but failed as well.
Only when Sesshomaru appeared again a day later did he easily suppress the sword's evil aura with his formidable strength and claim Tōkijin for himself. Throughout the early and middle stages, this evil sword forged from a demon's teeth accompanied Sesshomaru for a long