It's the year 305 of the Alcian calendar, and the world is currently controlled by "numbers." Every human born is branded with a "Count." This Count can be anything; the amount of kilometers walked, or the amount of people who have said your food is tasty. If your Count drops to 0, you will be sent into the Abyss. After Hina's mother's Count dropped to 0, her last request was for Hina to look for the Legendary Flying Ace.