Eiol, a world where strength matters but teamwork and planning is also essential. After all unlike other worlds in the vast multiverse, here every person has at least one partner to grow in strength with. Summons, Espers, Guardian or Eidolons. These are the many names that had been used in the past to refer to those partners.
The story follows Adrien, a regular teenager with the hope of becoming strong enough to overcome the hardships of the world and to avenge the wrongdoings committed to both him and his mother.