Shironeko Project ZERO CHRONICLE

In a world consisting of numerous isles, a young hero from the Astora Isle encounters the adventurer Kyle and follows him on an expedition on the isle. They meet a mysterious girl named Iris and a talking white cat, and together they make their way to the isles ruins, where they find a flying island. Kyle becomes consumed by darkness there, and the party resolves to travel to the ends of the world on the flying island in order to find the seven "Great Runes," following Kyles words before he disappeared.