Shy misfit Sio Ogura, who prefers talking about tanks instead of girl gossip stuff, has as her only friend the popular, kindhearted Asao. Sio has had reoccurring dreams of ancient battle scenes, but her life abruptly changes when a school trip is interrupted by an attack by Evolutionary Invaders, hideous alien creatures bent on conquering the planet. While attempting to rescue Asao, Sio discovers that she's an E-Gene Holder, a historical figure's reincarnation who can summon special weaponry. Her weaponry is of the legendary warrior Oda Nobunaga.
The Gastrea virus quickly spread as infected hosts gained new powers and abilities with each rapid mutation even while attacking, killing, and infecting multiple new hosts. Unable to fight such a pandemic, the remaining humans retreated into cities surrounded by giant monoliths made of Varanium, one of the few materials that can stop the Gastrea. Now mankind's last hope is the Cursed Children, infected young girls who have retained their humanity. Paired with a human partner, they alone have the strength to combat a Gastrea, but their power makes them feared and shunned by most humans.
Long ago, a valiant Band of Heroes using Ars Magus, a potent combo of magic and technology, defeated an insidious black beast endangering humanity. Ragna Bloodedge, a famous rogue outlaw, armed with the mighty Azure Grimore, now seeks to wreak havoc upon the Librarium, a clandestine organization that governs Ars Magus. Ragna soon becomes the target of bounty hunters, vigilantes, scientists, vampires, and Librarium foot soldiers, but he's unaware how closely his fate is tied to the world's future.
After a mysterious light transports Oda Nobunaga and other warrior girls from a parallel world to Earth, they find themselves stranded in a strange land full of technological gadgetry. They must adapt to survive, and some of them are finding it easier than others. But unlike the other girls who are slowly deciding to stay, Nobunaga wants to return to her world. Her only key to doing this is by collecting the "Secret Treasures" that all of the girls possess.
All Tatsumi wanted when he went to the capital was to make money to help his village. After he is rescued from a horrible fate by the assassins known as Night Raid, he is thrust into the middle of a bloody revolution between Prime Minister Honest (using his secret police, elite assassin squad, and the Empire’s armies) and Night Raid and a handful of rebels desperate to overthrow the brutal corrupt regime of Honest's puppet emperor. Wanting to help innocent people against this ruthless regime, Tatsumi joins Night Raid.
High school student Furuya is totally obsessed with zombies and even has a bizarre dream of having a zombie girlfriend. After his beloved pet cat is killed, he decides to make a potion mentioned in a strange book to reanimate it. Furuya accidently encounters Rea, a pretty girl who is miserable due to her creepy domineering father, and they slowly become good friends as she finds happiness with him. But they are unaware of the fate they will soon share.
At Areisha Academy prospective students learn how to form contracts with Spirits and must be pure, chaste, of superior lineage, and female, as the Demon King was the only man to make a Spirit contract. Shortly after Kamito Kazehaya (who is male and is going to the Academy at the Headmistress's request) encounters Claire Rouge, a student there, he protects her from an uncontrollable Spirit, which he somehow makes a contract with. His enrollment and Spirit contract create chaos, confusion, and even misunderstandings with the female students.
