The Tetsusaiga is a sword forged from Inuyasha's Father's Fangs By Totosai. The sword had been held in a cave where Inuyasha's father died for some time. Inuyasha and his much older brother Sesshoumaru fought over the sword. Neither one of them could pull it out of the ground. However, Kagome pulls it out with easy. Seeing how she is on Inuyasha's side, he gets the sword. The sword eventually gets broken by Goshinki ( A big, fast moving, mind reading demon). When Tetsusaiga is saprated from Inuyasha and he is hurt really bad, he transforms into a full blooded demon. Later on the Tetsusaiga gets reparid with Inuyasha's fang. This fuses Inuyasha and his fathe's fangs together making the sword more powerful and much heavier.
Submitted by Venom