Thanks to the Fruit of Evolution, Seiichi Hiiragi's amazing new life in another world allows him to meet dependable allies and create formidable spells. His abilities catch the attention of Barnabus Ablitt, the principal of the Barbador Academy of Magic, who invites Seiichi to become a teacher at the institution. Coincidentally, Seiichi's classmates from Earth are enrolled there, which will lead to an awkward reunion if he is to meet them. Behind the scenes, however, an enigmatic cult called The Great Devil Order devises a sinister scheme to resurrect their deity and sacrifice the students of Barbador to hasten the process. As Seiichi's power is second to none, it is up to him to protect not only his friends but also the entire world from the looming darkness.

The first short story focuses on Favaro and Kaiser between the events of the first and second series as they visit Favaro's home village. The second short story shows Kaiser as a knight commander sparring with Jeanne, and sharing the reasons they remained as Orleans Knights in the aftermath of the final battle against Bahamut.

Thousands of years ago, the ancient dragon Bahamut wrought havoc upon the land of Mistarcia, a world where both gods and demons live amongst mankind. Working together to prevent the world's destruction, the rival deities barely managed to seal Bahamut, agreeing to split the key between them so that the dragon would remain eternally imprisoned. With the world safe from the destruction of Bahamut, it is business as usual for bounty hunters like Favaro Leone. Living a laid-back, self-serving lifestyle, the amoral Favaro goes about his work while on the run from fellow bounty hunter Kaisar Lidfard, a righteous man who swears vengeance upon Favaro. However, Favaro's carefree life is thrown into chaos when he meets Amira, a mysterious woman who holds half of the key to the world's fragile peace. Shingeki no Bahamut: Genesis tells the story of a group of unlikely heroes who find themselves caught in the middle of an epic clash between gods and demons, forced to carve their own path in the face of the imminent storm.

A decade ago, humans, gods, and demons joined forces to stand against the threat of the colossal dragon, Bahamut. Now, in the present, humans living in the capital city of Anatae have been enjoying lavish and prosperous lives. Their progress is largely due to the administration of the newly appointed king, Charioce XVII, who has stolen a power from the gods and allowed for the abuse and slavery of the demon race in the capital. As humans continue to immorally exploit demons, a sense of hostility against humans begins to build up within demon communities, threatening a revolt. Meanwhile, an atmosphere of uneasiness is spreading among the gods, as they scramble to regain their lost power. Amidst it all, Nina Drango, a cheerful young bounty hunter, has arrived at the Royal Capital with hopes of settling down and earning a living. However, her peaceful life in the capital is quickly thrown into chaos when she crosses paths with the ominous Rag Demon who is determined to seek revenge against humans, and Kaisar Lidfard, a noble knight battling an internal moral conflict. Shingeki no Bahamut: Virgin Soul continues the tale of the social and moral conflict between humans, gods, and demons, and their struggle for survival and dominance.