The movie stops treating Inuyasha's parents as a dead plot device and makes them real, which means watching him understand where his anger actually comes from hits different than any TV arc. The animation jumps three tiers above the series, and the swordfights carry weight because they're not just cool, they're settling something that's been broken for 700 years. This isn't filler spinning the show's wheels. This is the kind of backstory that rewrites how you see the entire franchise.

A legendary sword awakens after seven centuries under seal, and trouble follows. Inuyasha's father left one of his swords to each of his two sons, but he locked a third blade, the wrathful Sou'unga, away. While visiting Kagome in modern times, Inuyasha comes across it at the Higurashi shrine, where it has been kept as a treasured artifact since one of her ancestors found it in the old well. The sword soon shows that it houses an evil spirit with a craving to kill. Inuyasha brings it back to the feudal era and clashes with his brother Sesshomaru, who has long wanted it. When the blade slips away during their fight, the brothers race each other to find it. Soon everyone is after its power, but the sword seems to have plans of its own, and its awakening threatens all of humanity. The rivals must put aside their differences in an uneasy alliance. The film blends adventure, comedy, drama and fantasy.