A very famous singer named Sachiko Kobayashi is suddenly summoned to another world at the moment a demon king’s castle is being overrun by heroes. Just as the demons face certain annihilation, a stone statue in which the demon king was sealed begins to glow, and Sachiko appears. She is immediately revered as the new demon king by the surviving demons. However, due to the shock of the summoning or the overwhelming tension, Sachiko has forgotten all her songs.

Despite this major setback, she possesses an overwhelming and powerful voice that is enough to drive away the invading heroes. Sachiko then sets out on a journey across the ravaged demon world. Her goals are twofold: to revive the demon world that the heroes have destroyed, and to recover her lost memories by reviving a middle boss. As she travels, she slowly regains her signature songs one by one, with each song unlocking more of her true power. The story follows her non-traditional quest to rebuild the realm using her spectacular costumes and singing, blending musical entertainment with the fantasy genre. A notable narrative arc involves encountering the group of heroes who first attacked the castle, who are portrayed as deeply unlikable characters.