After dying in a bus accident, overworked salaryman Arihito Atobe awakens in Labyrinth Country, where newcomers become Seekers by choosing their own job classes. Hoping for a peaceful second life, he instead finds himself saddled with an unprecedented Rearguard class whose true identity cannot even be deciphered by the Seekers Guild.

As Atobe assembles a party and ventures into the country's labyrinths, he gradually discovers that his mysterious abilities possess extraordinary support capabilities. Yet with neither allies nor enemies able to understand the full nature of his class, mastering its hidden potential may prove to be his greatest challenge.