In the beginning of human society, things were proceeding pretty well. The Animal Lords, an assortment of powerful and spiritually charged totem animals, monitored the comings and goings of animals and people all over the world. Then from somewhere unexpected and unexplained, possibly outer space, a figure of great power appeared named Mikado 52. Upset and jealous that the world was already teeming with life, he hid, sulked, and planned some sort of long game of spite against the world's inhabitants.

At some point, the four strongest members of the animal lords interbred with humans in order to experiment with their bloodlines.

As the human race grew, they started to communicate less and less with the animal lords, eventually abandoning them as they concentrated more on themselves. Eventually they forgot about them altogether. The animal lords wished to do something about this, but didn't really know how to present themselves to their human charges. Then, gradually, over a short period of time they began to grow bitter, angry and warped in mentality and form. Before they could realise what had happened, the titan poison had already taken effect.

At around about the same time in Japan, a large corporation named VEGAS appeared, and insinuated itself into many public walks of life. They became a family name, and were responsible for many helpful things for the lives of civilians. Public aid, media and economics, transport and so on were all stamped with the VEGAS logo. As a result, it would seem logical that when danger faced the Japanese public, VEGAS would also take an interest in it.

The animal lords had returned, and the titan poison with them. VEGAS began to execute a fight against them that lingered just on the edge of public knowledge. The poison had the ability to transform normal humans into creatures called 'Roaches', monsters that fought against other humans. At the same time, a new board of twelve staffmembers appeared in charge of VEGAS. They warned the public that some sort of criminal element was targetting people.

As a result, they announced that three new 'super heroes' would be protecting VEGAS' interests, led by Tokiwa Ishida, the Ace of Poker. The other two were the Ace of Blackjack and Ace of Solitaire. What the public didn't know was that Tokiwa Ishida was secretly Mikado 52, taking on a human role and a disguise not as the supreme leader of VEGAS, but a low-ranked enforcer. The titan poison had been his doing, and the twelve members of VEGAS were twelve of the strongest animal lords.

The only surviving animal lords to escape the titan poison sought out four girls- the only surviving descendants of the four strongest lords- to empower them. The animal lords had to be sealed and purified to stop them turning more humans into monsters. The members of Royal Flush now had to face off against both the animal lords and the attentions of VEGAS and Ishida.