Neo Kyoto is a place where everything is decided through the card game Build Divide. From resolving personal conflicts to determining social status, success in Build Divide means success in life. The biggest ambition of every player is to become the King, whose peerless skills grant them near-total rule over the city. One day, a young man wakes up in Neo Kyoto—with the knowledge of just his name, Teruto Kurabe, and carrying only a deck for a card game he no longer knows. Teruto soon encounters another player, Sakura Banka, who helps him remember both how to play Build Divide and his original mission: that no matter what, he must meet the King. Teaming up together, Teruto and Sakura find that their best chance for a royal audience is with the Rebuild tournament, where the one who collects twenty-one tokens from other competitors can challenge the King for their throne. However, as Teruto continues to play, he begins to regain his lost memories that call into question the very nature of Neo Kyoto.

In the wake of an earthquake that devastated most of the city, Tokyo has been rebuilt in record time due to the development of humanoid robots known as boomers. After the disaster, these machines now service the city as cheap labor. Genom Corporation is the mastermind behind the boomers, having become so rich and powerful that they have extended its influence into space. However, all is not well with the boomers. Random breakdowns in their neural structure are causing some of them to go berserk, destroying property and killing humans in violent rampages. To combat this, Tokyo has formed the Advanced Police, a peacekeeping force with jurisdiction over boomer matters. There are also rumors of a second group known as the Knight Sabers, a vigilante unit operating from the shadows. Trying to investigate the Knight Sabers, the adventurous Linna Yamazaki travels to Tokyo in pursuit of her heroes. There, she finds the enigmatic singer Priscilla Asagiri, the beautiful entrepreneur Sylia Stingray, and the exuberant Nene Romanova, each with their own reasons for coming together. As the struggle intensifies, the girls learn that the boomer problem might delve deeper than any of them could ever imagine.

Despite their differences in position, three men—the youngest senior executive of the Port Mafia, Osamu Dazai; the lowest ranking member, Sakunosuke Oda; and the intelligence agent, Ango Sakaguchi—gather at the Lupin Bar at the end of the day to relax and take delight in the company of friends. However, one night, Ango disappears. A photograph taken at the bar is all that is left of the three together. Fast forward to the present, and Dazai is now a member of the Armed Detective Agency. The Guild, an American gifted organization, has entered the fray and is intent on taking the Agency's work permit. They must now divide their attention between the two groups, the Guild and the Port Mafia, who oppose their very existence.

The slice-of-life battle story is set in a future that has neither World War III nor an alien invasion—just an ordinary future set after our current age. In this world, robots are part of everyday life, and they contribute in various aspects of society. Shinki are 15-centimeter-tall (about 6-inch-tall) cute partners made to assist humans. Equipped with intelligence and emotions, they devote themselves to serving their Masters. These Shinki can even be equipped with weapons and armor to fight each other. Such Shinki are named Busou Shinki (literally, armed divine princesses). In particular, the Shinki Ann (Arnval), Aines (Altines), and Lene (Altlene) serve a high school freshman named Masato. Things change when a new Shinki, the bellicose Strarf, joins them. (Source: ANN)