Office worker Yoshida has been crushing on his coworker, Airi Gotou, for five years. Despite finally scoring a date with her, his confession is promptly rejected. Drunk and disappointed, he stumbles home, only to find a high school girl sitting on the side of the road. The girl, needing a place to stay the night, attempts to seduce Yoshida. Despite rejecting her advances, he nevertheless invites her into his apartment. The next morning, the girl, introducing herself as Sayu Ogiwara, reveals that she has run away from Hokkaido all the way to Tokyo. During her six-month spree, she continually traded sexual favors for a roof over her head. Yoshida, however, remains unswayed by her seduction. Instead, he has her do a different kind of work—one that entails washing dishes and doing laundry. And so, a touching relationship between a heartbroken adult and a runaway high school girl begins.

World-class medical researcher Kanji Yakutani lost his little sister to a tumor years ago due to ineffective treatment. To honor her legacy, he has dedicated his research to developing new medications for such conditions. But as fate would have it, he overworks himself and passes away at the age of 31, only to be given a second chance at life in another world. When he wakes up, Kanji finds himself in the body of a 10-year-old boy named Falma de Médicis, the son of an esteemed family of medical practitioners in the Sain Fleuve Empire. Bearing the mark of a deity's divine blessing, Falma is capable of performing a unique divine art, allowing him to create and reduce any substance with the knowledge of its chemical properties. After reading through some pharmacology books, Falma realizes that this world is operating on similar medical practices as in ancient times. He also learns that medicine is an exclusive privilege to the nobility, depriving commoners of proper medical care. Using the knowledge from his past life and the divine abilities granted to him, Falma resolves to make medicine available to those who need it—irrespective of class.

Mirai Kuriyama is the sole survivor of a clan of Spirit World warriors with the power to employ their blood as weapons. As such, Mirai is tasked with hunting down and killing "youmu"—creatures said to be the manifestation of negative human emotions. One day, while deep in thought on the school roof, Mirai comes across Akihito Kanbara, a rare half-breed of youmu in human form. In a panicked state, she plunges her blood saber into him only to realize that he's an immortal being. From then on, the two form an impromptu friendship that revolves around Mirai constantly trying to kill Akihito, in an effort to boost her own wavering confidence as a Spirit World warrior. Eventually, Akihito also manages to convince her to join the Literary Club, which houses two other powerful Spirit World warriors, Hiroomi and Mitsuki Nase. As the group's bond strengthens, however, so does the tenacity of the youmu around them. Their misadventures will soon turn into a fight for survival as the inevitable release of the most powerful youmu, Beyond the Boundary, approaches. [Written by MAL Rewrite]

In a time when the great war between five rival races for supremacy on Earth ended with humanity's victory led by the hero Sid, the world suddenly gets "overwritten" right before the eyes of a boy named Kai. In this rewritten world, Kai witnesses humanity's defeat in the war as a result of Sid's absence—where dragons and demons now rule the land, and Kai himself has become a forgotten existence to all humans. However, after encountering the mysterious girl Rinne, Kai resolves to break free from this rewritten fate. In a world without a hero, he inherits the sword and martial skills of the hero (Sid) and challenges the powerful enemy races that dominate the land.