In the magical realm of Aetheris, a dark power spreads, infecting Grimrune and threatening to destabilize the kingdom of Velandra. Amid a royal betrayal, the knight Cyrus Perseon claims his throne with ruthless ambition, vowing to conquer all realms. Meanwhile, in modern Japan, high schooler Hiroyuki Uyehara’s mundane life is shattered when he stumbles upon a mysterious girl, Lyra, hiding in his school’s janitor's closet. A powerful demon soon pursues them, speaking in an ancient language and revealing Lyra’s royal heritage. As they try to escape, Hiro's latent power awakens, transforming him and unleashing a fierce strength he doesn't fully understand. Now bound by fate and magic, Hiro and Lyra must navigate a world where myth collides with reality, unaware of the deeper forces driving them together—and the dark trials that await.