[PROTECT THE SECRET]

​In a world where only 12% of the population is born with extraordinary elemental powers, possessing magic is a death sentence. Feared as a global threat, superhumans are systematically hunted and executed at a young age. In a desperate bid to save her four daughters, a dying mother cast a powerful, ancient seal, locking away the world's most formidable magic inside four simple butterfly hairpins.
​Years later, the Butterfly Sisters-Kanae, Shinobu, Kanao, and Aoi-are celebrated across the city for their immense medical intellect. But behind their flawless, fake smiles lies a hollow reality. Separated as children and subjected to horrific, traumatic environments, they were stripped of their ability to feel. Kanae is trapped in a cage of absolute anger, while the younger three feel nothing at all. Even after being rescued and adopted by Gyomei, the sisters remain completely oblivious to the world-ending magic resting in their hair.
​But a dark storm is gathering. Muzan Kibutsuji and the sinister Dark Clan have begun a terrifying ritual, sacrificing lives to raise an unstoppable army of the walking dead. To stand a chance against this ultimate evil, the legendary elemental factions-including the fierce Water and Wind clans-must unite.
​Yet, the key to saving humanity lies entirely with the Butterfly Sisters. To shatter the seals on their pins, they need more than just a combination of elemental forces; they must possess pure hearts and completely restore their lost emotions. With dangerous inner demons fighting to break free from within them, the sisters must face their deepest past traumas, learn to love and feel again, and reclaim their humanity before the darkness consumes everything.