For 16 years since her birth, El, a high school girl, lived as a perfectly ordinary girl. She led an unremarkable daily life, but one day, she began to hear a strange "sound" that only she could perceive. Around that time, she was discovered by the demon Amon, who calls himself "Lord Lucifer's loyal servant." El learns that she is a "vessel" destined to inherit the power of the Fallen King Lucifer, an existence born to fight against the False Gods. Confronted with a duty far too removed from reality, El struggles to comprehend the situation. However, around that same time, the False God's vanguard, Seraphim, sent by the False God Yaldabaoth through a crack in the seal, materializes and begins attacking the city. The "sound" El had been sensing was, in fact, a harbinger of the Seraphim's appearance. Forced by Amon to take up a weapon, a bewildered El nonetheless confronts the Seraphim to save her friends in the city—