At the Battle of Sekigahara in 1600, Toyohisa Shimazu is the rearguard for his retreating troops, and is critically wounded when he suddenly finds himself in a modern, gleaming white hallway. Faced with only a stoic man named Murasaki and hundreds of doors on both sides, Toyohisa is pulled into the nearest door and into a world completely unlike his own. The strange land is populated by all manner of fantastical creatures, as well as warriors from different eras of Toyohisa's world who were thought to be dead. Quickly befriending the infamous warlord Nobunaga Oda and the ancient archer Yoichi Suketaka Nasu, Toyohisa learns of the political unrest tearing through the continent. Furthermore, they have been summoned as "Drifters" to fight against the "Ends," people who are responsible for the creation of the Orte Empire and are trying to annihilate the Drifters. As the Ends grow more powerful, so does the Empire's persecution of elves and other demihumans. It is up to Toyohisa and his group of unconventional heroes to battle in a brand-new world war to help the Empire's subjects, while protecting the land to claim for themselves and challenging the Ends.

Five years ago, a mysterious phenomenon known as the Global Synchronic Urban Disappearance caused a large chunk of Ikebukuro to disappear overnight. Following the catastrophe, the inhabitants found themselves thrown into a state of disorder, and unexplained electromagnetic anomalies called "Auroras" began to be sighted. Awed by the performance of idol Izumi Hinazaki at a play utilizing the "Super Material Theater," a stage designed to revitalize Ikebukuro through hologram-enhanced plays, high school student Seria Morino is inspired to become an idol. Shortly afterward, she is scouted by a young woman named Kaoru Sakakibara, who turns out to be the director of Alice in Theater—the troupe that Izumi used to be a part of. Aiming to pursue her dreams, Seria decides to follow Kaoru and joins Alice in Theater. Upon arriving at their establishment, she is cordially welcomed by a group of young and friendly girls who are all very passionate about acting. However, something seems to be amiss…

"The Shepherd," an urban legend of Shiomi Academy, is said to appear before hardworking students to grant them a wish. While engrossed in a book inside the school's renowned Great Library, Kyoutarou Kakei, a second year student and the Library Club's de facto president, receives an email from the Shepherd foretelling an event that will change his fate. Worried by the message, Kyoutarou rushes over to a nearby train station and encounters fellow student Tsugumi Shirasaki, whom he saves from being hit by a derailing train. Grateful for his heroic actions, Tsugumi joins the Library Club and invites Kyoutarou to participate in her mysterious "Shiomi Happy Project." Together with other new members of the club, they strive to make the academy a better place and uncover the identity of the enigmatic Shepherd.

The story is set in December of 2199, when the streets are full of anticipation for the end of the year and the start of the new one. Amid the celebrations, word spreads that Ragna the Bloodedge, an SS-class rebel with the highest ever bounty on his head, has appeared in the 13th Hierarchical City of Kagutsuchi. The apparent aim of Ragna or the "Grim Reaper" is the destruction of the system controlling the world. To collect the bounty, a motley array of unrivaled fighters converge on Kagutsuchi. (Source: ANN)