Asato Kanami was summoned as a hero to another world, Istalia, to stop the war between the demons and humans. It is said that he was summoned by Anna, the Saint of the Kingdom of Elshnon. After a year of war, Asato finally challenges the Demon King, Lione. However, just when he thought the battle was over, his summoner Anna attacked both him and the Demon King. But Asato survived the attack and was protected by the Demon King. What is the future path for the hero betrayed by humans...!?