Despite having no real combat talent, kind 15-year-old Kurt Rockhans belongs to the famous party Flaming Dragon Fang. He is perfectly satisfied as the party's helper—until the other members kick him out and replace him with a stronger ally. Left without a way to provide for himself, Kurt begins searching for a job. With his job prospects limited by his lack of combat ability, Kurt gladly accepts any work that comes his way. During one such job, he meets Yulishia, an adventurer formerly employed by the royal family. Surprised by Kurt's impressive work, Yulishia discovers that he is no ordinary boy: Kurt possesses an astonishingly high aptitude in a variety of non-combat fields. Due to these talents, a court official tells Yulishia to offer Kurt a high status in the kingdom that would allow him to live in peace for the rest of his life. When Yulishia informs Kurt about his potential rank, he brushes off the offer, refusing to think of himself as above other people. Still unaware of his real power, Kurt continues taking as many odd jobs as possible, which might just make him a pivotal part of the kingdom before he even notices it.

For over one hundred years, a special quest has been waiting for a wizard skilled enough to complete it. On the northern continent of Guiltina, there are five immensely powerful Dragon Gods who possess great destructive force that can only be quelled by sealing them away. Natsu Dragneel and his friends from the Fairy Tail guild—Lucy Heartfilia, Gray Fullbuster, Erza Scarlet, Wendy Marvell, and the exceeds Happy and Charlés—consider this the perfect challenge to take on. The Fairy Tail mages are not the only ones searching for the Dragon Gods. Diabolos, a guild exclusive for "Dragon Eaters," seeks to enhance their Dragon Slayer magic by devouring the dragons. Meanwhile, Fairy Tail's newest addition, Touka, appears to be hiding something sinister from her new companions—and her secrets may bring disaster to the guild while its strongest wizards are away.

When Demon Queen Echidna begins her invasion of the human realm, the people turn to the hero Leo Demonheart to protect them. Blessed with insurmountable power, Leo easily repels Echidna's army, thereby saving the world. But instead of gratitude or admiration, Leo is met with disdain and scorn from his fellow humans, who fear his overwhelming strength and believe that it may eventually cause humanity's demise. Banished from the kingdom he once called home, Leo wanders aimlessly throughout the land until, one day, he hears rumors of Echidna's efforts to rebuild her army. Hoping that demonkind might accept him as an ally, he returns to the demon queen's castle and offers Echidna his help. Naturally, Echidna immediately rejects him. Still, not all hope is lost, as Leo manages to convince Echidna's four generals to let him secretly work under their supervision. Donning the identity of a masked dark knight named Onyx, Leo solves the demon army's problems one by one—gradually improving the quality of life around the castle. Above all else, however, Leo wants to accomplish one goal: to learn why Echidna started the war in the first place.

High school student Taiyou Asano has been socially inept ever since his family died in a car crash. The only person he can properly interact with is his childhood friend, Mutsumi Yozakura—the head of the world's strongest family of spies. Mutsumi's eldest brother, Kyouichirou Yozakura, has been overprotective of her ever since he once rendered her severely injured. His love for Mutsumi is lethal, and Taiyou is his next target. To survive, Taiyou must marry Mutsumi and become a member of the Yozakura family. Thrown headfirst into chaos, Taiyou begins his journey to become a powerful spy in order to protect his wife and uncover the dark secrets of his past and the Yozakura family.