in this world your number is given at birth and your given a rule count, every time your rule happens your number goes up but when your number goes to 0 you go to the abyss, a pure darkness of pain that no one knows whats inside, 2 people can wager there numbers in a battle in which the winner gains the number set for the dual, there is also a story about legendary aces that lived 300 years ago and had a white star next to there number and saved people in the "wast war"

you see her walking in town as she comes up to you

hina:"ha...hay...do you know a person called the legendary ace?"

you see her number is on her thigh and its 411