A twenty-five-year-old man named Yusuke Yahagi dies in a traffic accident and is reincarnated in a fantasy world of swords and magic. He is assigned the unique job of dagashiya, a traditional Japanese candy and toy shop. By simply willing it, he can summon a mobile storefront stocked with inexpensive snacks that carry minor magical effects, such as curry rice crackers that restore stamina or squid skewers that heighten the senses. Because the treats are both cheap and useful for dungeon exploration, his shop quickly draws a steady stream of rookie adventurers who become regulars.

Yahagi sets up his business in a kingdom centered around a dungeon, and his sales drive the shop itself to level up. The store evolves from a small cart into a full-fledged wooden two-story building with living quarters, and new abilities eventually manifest, including the rare magic of clairvoyance that lets him see distant locations as if through a live camera. Among his most notable customers is a lively pink-haired young woman named Meryl, who is actually the wanted witch Minerva in disguise. She was placed on the kingdom's wanted list after allegedly cursing the king, but she hides as an adventurer and becomes intensely attached to Yahagi, exhibiting possessive yandere behavior. Another recurring patron is a mysterious man in a silver mask whose true identity remains ambiguous.

As Yahagi becomes more comfortable with his new life, the scope of his business expands beyond the shop itself. He organizes game tournaments, creates a hot spring facility, and finds his snacks and toys drawn into larger events. The narrative's turning point comes when a royal proclamation is posted on the town bulletin board, revealing that the kingdom's fate may hinge on the toys sold at a simple dagashiya. For the first time since his arrival, Yahagi faces a genuine choice that will determine not only his own future but the direction of the country he now calls home. Over the course of three volumes, the story blends slice-of-life commerce with light fantasy, following Yahagi as he runs his shop, builds relationships with adventurers and commoners alike, and gradually earns the trust of a world that has never seen anything like a dagashiya before.