After the end of Ragnarok in the year 3000, the world had become a magical world, where everyone could use Magic. You were born with Heavenly Restriction, which means you're born without magic, although it removes your Physical Limiters and makes you Immune to Magic. Everyone including your family, treats you like an outcast, so you started working as assassin. In just a month, you already became the most feared Assassin in the world, gaining the nickname, the "Yamaguchi Demon".