A high school student named Hayato Katsuragi dies in a traffic accident and is reincarnated in a fantasy world of swords and magic as Reivelt Runwalker, the son of a noble family. A goddess grants him a cheat skill with no level limit, allowing him to grow stronger without restriction. However, she also saddles him with the devastating title skill The One Afflicted by Hardship, which guarantees that his new life will be beset by constant danger and crises. Determined not to die young again, Reivelt reveals his identity as a reincarnated person to his parents and begins rigorous training alongside his half-sister Aelis and his father's third wife Eileen. The peaceful days of family life, cute maids, and a younger sister are shattered when the warning bells ring: a great monster march, a massive horde of beasts that occurs only once every several decades, is about to descend upon the region. Reivelt must rely on his boundless growth potential to defend his home and prove his strength. After repelling the monster march, he travels to the royal capital to report the incident, where he is challenged to a mock battle against a hundred soldiers to verify his achievements and catches the attention of a battle-hungry princess who demands a duel. The narrative follows Reivelt's journey as he confronts increasingly severe threats orchestrated by human schemes and ancient evils, growing through each ordeal while building bonds with family, allies, and the kingdom's leadership. The overarching conflict ultimately leads him and his companions to face the demon gods responsible for the world's turmoil, culminating in a final battle where Reivelt sacrifices himself to defeat the demon god Baron. Three years later, the goddess appears on the anniversary of his death and revives him, bringing the story to a close.