The protagonist, Kyoji Himuro, finds himself unexpectedly transported to another world after a mundane trip to the convenience store. Initially disoriented and lacking any special abilities or money, he quickly faces the harsh reality of survival. After a terrifying encounter with a bird-like monster, he reaches a fantasy-esque town. His attempts to check his status at the Adventurer's Guild are thwarted by his lack of funds, leading to his expulsion. Facing starvation, Kyoji resorts to scavenging for food from a restaurant's garbage, where he discovers seeds.
Inspired by this, Kyoji decides to cultivate these seeds, believing them to be vegetables. He finds a secluded spot outside the town with a dilapidated shed and begins his farming endeavor. To his surprise, the seeds sprout rapidly, growing into plants that quickly mature into what he initially perceives as large vegetables. However, these "vegetables" reveal themselves to be aggressive plant-type monsters, which he dubs "Killer Plants." Just as he realizes his mistake, a young, feisty girl knight named Lily intervenes, destroying the monsters.
Lily scolds Kyoji for cultivating dangerous monsters, but he claims ignorance, believing them to be vegetables. This leads to a revelation: in this world, all plant life originates from monster seeds, and "vegetables" as Kyoji knows them do not exist. Lily, whose brother is a park guard, was sent to warn him after complaints about his unusual activities. Recognizing Kyoji's predicament and the scarcity of edible monster parts, Lily proposes an alliance: Kyoji will cultivate monsters, and she will help harvest them, sharing the spoils.
Their first joint venture involves cultivating "Jack-o'-lanterns," a less aggressive pumpkin-like monster. They acquire seeds from a dead Jack-o'-lantern in a nearby forest dungeon. Kyoji, now equipped with tools purchased with Lily's brother's money, successfully cultivates a patch of Jack-o'-lanterns. Lily helps harvest them, and they take them to a small, struggling diner run by a girl named Mina, who is Lily's friend. Kyoji agrees to supply Mina with his cultivated monster parts at a reduced price to help her business, and in return, they are treated to a meal of Jack-o'-lantern soup and Killer Wolf stew.
Kyoji's ambition grows, and he decides to cultivate Mandragoras, which are rare and valuable. Lily warns him against it, but he proceeds. To his surprise, the Mandragoras, when harvested, do not become mere screaming roots but transform into small, naked, crying, humanoid figures who beg for their lives. Kyoji, unable to kill them, decides to let them live in his garden, much to Lily's resigned amusement. Meanwhile, a shady merchant overhears about Kyoji's success with Mandragora cultivation and sells the information to a group of rough-looking adventurers, who then head towards Kyoji's secluded farm.
