Inuyasha the Movie 4: Fire On the Mystic Island

Within the dark recesses of Horai Island, a group of half-demons live under the demonic rule of the Four War Gods. Escaping with barely a shred of hope, Ai, the youngest of the half-demons, returns to the island with Inuyasha, who must face not only the Four War Gods, but the past he left behind on the island fifty years ago.