After a decade spent fighting monsters in the Shadow Labyrinth—a growing dark cloud of magic that threatens to engulf the world and destroy all life—mage Desir Herrman and his five companions finally face their last foe: the dragon of destruction Boromir Napolitan. Although the group of heroes manages to slay this formidable opponent, the tremendous amount of mana stored within the dragon's body is released in an unstoppable explosion that annihilates the rest of the world. However, instead of dying, Desir is sent back 10 years into the past with complete memories of events to come. He enrolls at Hebrion Academy, determined to put an end to the classist prejudice plaguing the magical world that will ultimately lead to the demise of humanity. Unfortunately, his struggle begins early on during the entrance exams; although he is ranked first of his group, Desir is assigned to the Beta Class, the default class for commoners. Now, Desir's next objective is to rally someone to his cause that he could not save in his previous life: the wind mage Romantica Eru. Then, Desir will have to show his worth to the Alpha Class with his newly formed party if he wants to ultimately save as many lives as possible.

On November 23, 1957, the whole world witnessed the Federal Republic of Zirnitra's monumental achievement of sending the first live animal—a dog—to outer space. Since then, the space race between the confederacy and its competitor, the United Kingdom of Arnack, has intensified; the two countries hope to one day send humans to the cosmos above. As a dog's biology is inherently different from a human's anatomy, there is no way to perfectly identify the risks involving space travel and its effects on an individual's body without actually sending someone for observation. However, Zirnitra's government has a potential solution: to experiment on vampires, whose biological similarity to humans is too significant to ignore. Despite being forcibly taken from her home in the mountains, vampire Irina Luminesk shows no resistance and is even willing to train as a test subject. Lev Leps, a former top candidate to become the first human cosmonaut, is designated to accompany Irina and act as her guide. Through their time together, Irina and Lev begin to develop a mutual love for outer space, bringing them closer together.

After years of conflict, humans and monsters have settled their differences and are now at peace. This post-war era led to the foundation of Lindworm—a town which has since become the focal point of racial harmony. As a human doctor specializing in monster biology, Glenn Litbeit runs a small clinic alongside his partner, Saphentite Neikes, who is a half-snake monster known as a lamia. He uses his knowledge to tend to any monsters who seek his aid. Whatever affliction, concern, or injury it may be, he will always be there, ready to help.