When three complete strangers, Mishiba Toki, Nakajyo Nobuto, and Saitoh Kazuo, are hired by a corporation to compete in the Bus Game, an illegal dog-fight conducted in strict secrecy, they are given the team code of "Team AAA" (Triple Anonymous). This group of three who differ entirely from their living environments to their personalities have to work together effectively, but without mutually wiping out their mistrust of each other or prying into each other's privacy. They only have one point in common—each of them need a large amount of money for their individual circumstances. To get the money, they must play in the game despite their very own lives being at stake.

This world has gone through many Dusks, and is slowly nearing its end. Within this world, in the western reaches of the "Land of Dusk," there was a nation that prospered thanks to its use of alchemy. There, in order to survive the eventual arrival of the "Dusk End," the people devoted their efforts to rediscover and recreate lost alchemic technologies. Rediscovered technology from the past era was gathered in the alchemy research city known as "Central," where research was conducted on how to halt the advance of the twilight. One of the heroes is a young man who researched alchemy in Central, the other a girl living in a small town on the frontier. This girl's name is Escha. In the process of using her knowledge of ancient alchemy to help others, she was assigned to the Development Department. The young man's name is Logy. Having learned the newest alchemic techniques in Central, he requested a transfer to this understaffed town to make use of his abilities, and meets Escha when he is assigned to the Development Department as well. The two make a promise to use their alchemy together, and bring success to the Development Department.

In the bustling and futuristic city of Heartland, a young boy named Yuuma Tsukumo has a dream that everyone his age wants to achieve—earning the title of the greatest duelist! Sadly, due to his lackluster dueling skills, this dream is far from achievable. But when the school bully, Ryouga "Shark" Kamishiro, splits the key given to him by his father into two pieces, he inadvertently sets Yuuma on a collision course with his dream. Retaining one half of the key, Yuuma begins a duel with Shark, but soon realizes that his inexperienced skills are no match for him. In a sudden turn of events, Yuuma's key repairs itself, and the "Door of Destiny'' appears before him. Using the key to open it, Yuuma is greeted by an alien by the name of Astral—a being only he can see. The bewildered Yuuma soon learns that his memories have been divided into 100 "Number Cards," all of which he must retrieve. However, he is also not the only one looking for them. Bombarded by these revelations, Yuuma, alongside Astral, must defend the world from the upcoming threats that loom over Heartland City—regardless of any divine intervention that may occur.

Long ago there was a war in Heaven which resulted in Judas and Luca – two of the six specially-chosen, talented and strong Saint Beasts – being cast out and imprisoned in Hell for leading the rebellion. But before that Heaven had been a peaceful place where the angels happily lived their lives. In this time, Judas, Luca, Goh, Shin, Rey and Gai are adolescent angels in Heaven who, on the day of Benediction, are made into adults by the supreme god Zeus. With each of the six having their own special abilities and new adult bodies to get used to, opportunities to meet each other arise and new friendships are formed. (Source: Anivide)