InuYasha the Movie 4: Fire on the Mystic Island

Hourai is a mysterious island that appears every 50 years. Some believe it holds the secret to eternal life, while others fear it brings disaster. When Inuyasha's group saves a half-demon child named Ai from a monster, they learn she escaped from Hourai. Ai is an acquaintance of Inuyasha's and asks him to rescue her friends, who are being held prisoner by the Four War Gods, a dangerous enemy Inuyasha remembers. Arriving at Hourai, Ai's friends are horrified to find few orphans left, all destined to be sacrifices for the Four War Gods' power. The victims are marked by the demons, preventing their escape. Inuyasha decides to defeat the four demons, but their strength will require the group's combined efforts.