The sword So'unga, (which can translate to, "Amassing Cloud Fang") was not created by Totosai, nor was it forged from one of Inutaisho's fangs. The initial origin of the sword remains shrouded in mystery. What is known is that the sword is possessed by the spirit of an ancient demon dragon from hell. How Inuyasha's father came to acquire the sword is also unknown, but it is possible (if not likely) that he was selected to wield the sword as a means of controlling So'unga (like Sesshomaru controls the spirit of the Tokijin).

The movie shows the only time that Kagome ever feels the effect of her own "sit" commands (when she tries to prevent a possessed Inuyasha from killing Jaken and Rin).