The story begins with Haruto Riva, a seemingly ordinary high school student, encountering a beautiful goddess in a white void. She informs him that he has died in a traffic accident and is now in an interdimensional space. However, his soul is special, granting him a chance to live again with a powerful skill: absolute invincibility, meaning he will never take damage from any attack. The goddess, with a playful demeanor and a hint of embarrassment about her own physique, explains that he is free to use this power as he wishes. Before he can ask more questions, she is forced to end the conversation due to fading power, sending him back to his world.
Haruto awakens back on the street, unharmed, with the carriage driver nearby. He initially dismisses the encounter as a vivid dream, believing himself to be a normal student. However, his newfound invincibility is soon put to the test when a dragon, a formidable beast capable of destroying cities, attacks his hometown. Driven by a strange confidence and the goddess's words, Haruto approaches the dragon. He discovers his body is indeed impervious, emitting metallic sounds when he lightly strikes himself.
As the dragon breaches the town's defenses and unleashes a devastating black flame breath, Haruto is engulfed. Instead of dying, his invincibility skill activates, manifesting as a radiant angelic crest that repels the attack. He realizes the skill is real. Two young adventurers, the twin sisters Alice and Lilis, who are B-rank but bravely attempting to buy time for the town's evacuation, witness his survival. They explain that only S-rank adventurers can typically fight dragons and that they possess a rare item, "Magic Missile," which can defeat the dragon but requires significant charging time.
Haruto, understanding the danger and inspired by the twins' courage, decides to use his skill to draw the dragon's attention, allowing them to prepare their attack. He successfully deflects the dragon's breath and physical attacks, astonishing the twins and the dragon itself. He then proposes a plan: he will distract the dragon while they use Magic Missile to defeat it.
After the dragon is defeated by Lilis's Magic Missile, Haruto is praised by the twins, who introduce themselves and invite him to consider becoming an adventurer. They explain the world's ongoing struggle against monsters that appear from another dimension and the role of adventurers in combating them. Haruto, having never experienced such a strong sense of purpose or being needed, is deeply moved. He receives a substantial reward for his role in the dragon's defeat, and though he returns to his family, the experience has ignited a desire for a life beyond his ordinary student days. The narrative concludes with a glimpse of the goddess, Ilfaria, and other divine beings observing seven chosen souls, including Haruto, who have been granted powerful skills to influence an impending conflict between gods and demons. Haruto, now contemplating a future as an adventurer, is on the cusp of a life filled with challenges and the potential to make a significant impact.
