Faced with an imminent threat from Kimaira, Ryusuke is saved when his older sister Misa offers herself in his place. Driven to rescue her, he teams up with Mikoto, another victim of the creatures' attacks who has lost everything dear to her. The arrival of Byakko forces Mikoto to transform into the powerful Soul Eater, leading to a high-stakes battle against the formidable foe. Though the encounter ends in setback, it sparks Mikoto's unyielding quest for revenge.