From a great lost in her life, a girl scientist created a new substance called 'Metaphysic particle'. The substance has a power that what's in one's strong mind can become a real thing. Due to an accident, the substance got spread around the world. Afterward, monsters appear and create chaos around the world. People blame the girl and called her 'Witch' since they think that the monsters are resulted from the substance. Among mankind, there are some people who can use this 'Metaphysic particle'. They use strong power of mind to create a beast to fight with monsters. Afterward, they, who use 12 items to create those beasts, become known as TWELVE.
(Source: Baka-Updates)