FRACTALE

The story takes place on an island, where a "Fractale System" is beginning to collapse. One day, Clain finds an injured girl called Phryne under a cliff. She disappears leaving a pendant. Clain sets out for a journey with the girl-shaped avatar Nessa to look for Phryne and discovers the secret of the Fractale System. — Description from AniList community (anilist.co).