The Fated Day is the day in which the "I Prescelti Sette", the world's current "Strongest Seven", are transformed into Arcobaleno by shining a mysterious light on the seven. This process is usually brought about by a contracted job gathering the strongest seven together, or during a Representative Battle, where the members of the winning team are cursed.
Before the new Arcobaleno are cursed to protect the Arcobaleno Pacifiers, Checker Face removes the Arcobaleno Pacifiers from the previous Arcobaleno. Usually, the strain is too much for the former Arcobaleno, and they die, but some manage to survive. However, the survivors live a cursed life afterwards, and all former surviving Arcobaleno become one of the Vindice.