If you loved Inuyasha the Movie 4: Fire on the Mystic Island, try Inuyasha the Movie 3: Swords of an Honorable Ruler
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.

Inuyasha the Movie 4: Fire on the Mystic Island

Inuyasha the Movie 3: Swords of an Honorable Ruler
What they share
Both films are directed by Toshiya Shinohara, and they both carry the foreign gem, uplifting mood tags, and they sit in Adventure / Animation / Fantasy territory. If that's the register that drew you to Inuyasha the Movie 4: Fire on the Mystic Island, the second film will land in a comparable space — through a different lens.
What Inuyasha the Movie 3: Swords of an Honorable Ruler is
Inuyasha if family drama fueled world-ending stakes. The dog brothers inherited swords from their father, but the most dangerous one got locked away. Now Sō'unga has resurfaced, and sibling rivalry might be the only thing that can stop it. A solid entry for fans.