The love between brother and sister. The love between man and woman. That which is most forbidden is most unyielding. The two sons and five daughters of the Shiunji family shine like brilliant gems, each with intelligence and beauty in equal measure. And with the pedigree of their wealthy father behind them, how could they not be the talk of the town? Eldest son Arata has spent his life being tossed around by the whims of his colorful sisters, yet a little teasing won't stop him from valuing his family over anything and anyone else. But when his youngest sister turns fifteen, their father reveals a long-hidden secret of the Shiunji "siblings" and knocks Arata's world off its axis...

With its flickering streetlights, moldy back alleys, and noisy populace, the Second Kowloon Walled City, despite the squalor of its already-demolished predecessor, evokes a special kind of nostalgia that its residents find endearing. Amidst the walls of this fading yet beloved landscape lives Reiko Kujirai, a 32-year-old realtor deeply in love with her coworker, Hajime Kudou, who is two years her junior. Though they have their differences, the two get along well enough to experience the joys of the walled city together. However, everything starts to fall apart when Kudou, half-asleep, suddenly kisses Kujirai—seemingly reciprocating the feelings she has yet to confess. But when Kudou explains that he had mistaken her for someone else, Kujirai finds herself drawn into a series of events that lead her to a past she cannot remember.

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?