Totosai , is an elderly blacksmith demon who forged Tetsusaiga and Tensaiga from the fangs of his old friend, The Great Dog Demon, who entrusted him to help his two sons. As InuYasha grows stronger and Sesshomaru grows more compassionate, they become more capable of mastering their respective swords, which Totosai strengthens accordingly. He spends most of his time at his forge inside a volcano, but sometimes travels elsewhere on a flying three-eyed ox named Mō-Mō.
Totosai often appears to be a cowardly, absent-minded old man, but he has the strength to pause an attack from Sesshomaru long enough to allow InuYasha to get away; he can breathe fire and his giant forge hammer can open large fire pits in the ground. At the end of the series, he continues his role as a blacksmith as seen when giving Kohaku a new weapon.