Takeru Kamishiro is an exhausted Japanese salaryman whose life ends abruptly, only for him to wake up before a god. This divine being reveals that the magical planet Madeus has suffered repeated civilizational collapses due to the poor decisions of its inhabitants. To break this destructive cycle, the god reincarnates Takeru into Madeus as an outsider with enhanced knowledge and problem-solving abilities.

Reborn in a younger, taller body with immense magical power and a set of unique skills, Takeru is given abilities including physical enhancement, immunity to disease, fear resistance, exploration magic, spatial magic, and a special power to search for and analyze valuable materials. Rather than pursuing glory as a warrior or hero, Takeru chooses a humble profession as a material gatherer, using his search ability to collect herbs, ores, monster parts, and other resources while traveling the world at his own pace.

The world of Madeus is a classic fantasy realm of swords and sorcery, populated by humans, elves, lizardmen, divine beasts, and ancient dragons. Takeru begins his journey near Tormi Village, taking on gathering quests from local merchants. During an expedition to the Eastern Mountain to collect misril ore, he accidentally disturbs Voldius, an ancient black dragon and one of the four great beings who watch over the world. Impressed by Takeru's magic, which surpasses his own, Voldius asks for help with an egg tainted by miasma that cannot hatch. Takeru pours his magic into the egg and successfully hatches a baby dragon, whom he names Bee. Voldius entrusts the hatchling to Takeru's care, linking Takeru's magic bag to an underground lake infused with dragon magic essential for Bee's growth.

As Takeru travels, he forms a party of unique companions. Bee, the ancient dragon cub, is adorable but has a distinct fishy smell and a huge appetite, using spirit skills to control fire, water, wind, thunder, and light. Brolite is an elf skilled with dual daggers who Takeru rescues from starvation while she searches for a rare white horse; despite her beautiful face, she is mischievous and frequently gets dirty. Clayston is a veteran lizardman adventurer from Belkaim City who befriends Takeru and, after being healed with magical lake water, temporarily evolves into a Dragonewt. Hofvalpnir, nicknamed Pnir, is a divine horse who served as the guardian of a lake, constantly absorbing toxins until she turned to stone; Takeru purifies the lake, awakening her, and she joins his travels by taking human form.

Notable narrative arcs include Takeru's early establishment in Tormi Village, where he balances gathering work with raising Bee and learning the extent of his powers while remaining largely oblivious to just how overwhelmingly strong he truly is. His encounter with the starving elf Brolite leads to her becoming his bodyguard. Later storylines involve healing corrupted lands and ecosystems, including purifying a lake poisoned by impurities, which restores the divine horse Hofvalpnir. An arc involving elves reveals that a supposed curse plaguing their population is actually a genetic disorder caused by generations of inbreeding to maintain bloodline purity, showcasing Takeru's modern scientific knowledge providing solutions that magic alone cannot. Throughout the series, Takeru's actions create ripple effects that reshape Madeus, attracting the attention of other gods who are not entirely pleased with how much he has already altered the world.