Arihito Atobe, a salaryman exhausted by the relentless demands of his inflexible superior Kyoka Igarashi, meets his end in a tragic bus accident. He awakens in the Labyrinth Country, a fantasy realm where the dead are reincarnated as Seekers, adventurers who explore dangerous labyrinths and must join a guild to survive. Given the chance to choose a new job class, Arihito refuses to repeat the mistakes of his past life by once again following Kyoka's brutal pace. Instead, he selects an unusual and often-overlooked support class called Rearguard, a role that operates from the back lines to enhance allies with critical attack, defense, and recovery abilities.

As a novice Seeker, Arihito quickly discovers that his chosen path holds unexpected power. Simply by positioning himself at the rear of the party, his abilities grow and his companions fondness for him increases. He forms a diverse party of adventurers, including Theresia, a masked lizardman rogue who cannot speak but shares a strong silent bond with him; Elitia, a short-tempered cursed blade wielder; Suzuna, a gentle shrine maiden who serves as the party healer; Misaki, a quirky gambler; and the merchant Madoka alongside the emotionless dissector Melissa. Complicating matters, his former boss Kyoka has also been reincarnated as a Valkyrie and seeks to work with him again, forcing Arihito to navigate their strained history while building a new dynamic.

The narrative follows Arihito and his party as they climb the ranks of the Labyrinth Country, starting from the lower districts and aiming for the top. A major early arc involves a chance encounter with a Hidden God named Ariadne, who grants Arihito even more formidable rearguard abilities. As they prepare to advance from the eighth district to the seventh, a crisis erupts when a deadly monster stampede from the labyrinth turns the town into a battlefield, forcing the novice Seekers to protect the populace. Throughout their journey, the party faces powerful named monsters, navigates the dangers of debuffs and mind-affecting traps, and contends with a constant persistence of evil that threatens not only Seekers but all inhabitants of the Labyrinth Country. The world operates under unique systems such as Karma, a law enforcement mechanic that punishes wrongdoers with imprisonment and forced labor. Arihito, determined to protect his newfound freedom and support his companions, must prove that true strength lies not in frontline combat but in the courage to sustain those who fight beside him.