After Jinta and Suzune ran away from their home as children, they were taken in by Motoharu—the virtuous sentinel of Kadono Village—and his daughter, Shirayuki. The settlement was ruled by its shrine maiden, Itsukihime, whom only a select few were allowed to interact with. When Itsukihime passed away, Shirayuki was appointed in her place. Wishing to stay in contact with her, Jinta worked diligently for years and was finally selected as the next sentinel. As the protector of the village, Jinta's duty is to eliminate any threats. One day, he encounters a demon in a nearby forest. At the end of the battle, the demon makes a proclamation about the destined ruler of all demonkind. He attaches his severed arm to Jinta, turning him into an unaging demon man. By the time Jinta comes to, Kadono is on fire. Suzune has transformed into the demon from the divination, and due to a series of misunderstandings, she murders Shirayuki and flees. Devastated, Jinta cannot forgive Suzune for her actions; he departs on a journey to find her. As Jinta travels around Japan across the eras, he endeavors to protect as many people as possible from aggressive demons. In his quiet moments, he contemplates what he should do when he once again faces his childhood friend.

Life hasn't been kind to Zenos. He was born in the slums, and his dirt-poor background has denied him almost every opportunity. After an encounter with a healer, he throws himself into studying to become one and finally catches a break when an adventurer invites Zenos into his party. Zenos is thrilled—so thrilled, in fact, that he's willing to put up with his teammates treating him like garbage. They fail to appreciate his talents and ultimately kick him to the curb, claiming he's outlived his usefulness to them. Now bereft of money and out of options, Zenos decides to put his self-taught skills to use elsewhere and opens an underground clinic. Word quickly spreads about the brilliant healer working incredible magic in the city's shadowy underbelly. Even the royal palace is taking notice... Can Zenos buck the odds and carve out a life for himself in a world that's spit in his face? And can he save the lives of the patients who wind up on his doorstep in the process?

In ancient times, some witches married their familiars, who had taken human form, giving birth to a lineage of ogres. One such ogre is Morihito Otogi, who while appearing completely human, still retains the inhuman strength of his bloodline. Nico Wakatsuki is a young witch and Morihito's childhood friend, but as part of her education, she had to go to the Witches' Holy Land to train and part ways with Morihito . Years later, just before Morihito's first year of high school, Nico returns home with one goal in mind: to claim him as her familiar. While most witches choose a cat or a bat, Nico has her heart set on Morihito in more ways than one. Although seemingly oblivious to her true feelings, Morihito and Nico end up living together under the same roof with both of Morihito's parents elsewhere. While reluctant at first, Morihito accepts his new role, determined to help Nico seamlessly fit back in with human society and protect her from fated disaster.

Beryl Gardinant, a self-proclaimed "humble old man," is a sword instructor at his dojo in a rural, backwater village. In his younger years, he dreamed of glory as a master swordsman, but those days are long behind him. Out of the blue, he receives a visit from a famous former pupil who brings him world-shattering news—he's been appointed as a special instructor for the knights of the Liberion Order! With his life now turned upside down, Beryl travels to the capital and reunites with some of his former students: elite knights, an ace wizard, and even an adventurer who's attained the highest guild rank possible. But why do they all want his tutelage?! As far as he's concerned, they clearly don't need him anymore. Can Beryl live up to his new position? And will he ever get a moment's peace away from his adoring students?!