The protagonist, Yamato, finds himself inexplicably transported to an unfamiliar forest. Realizing he is no longer on Earth due to the presence of two moons in the sky, he quickly assesses his situation. Yamato, an experienced outdoorsman, prioritizes survival, focusing on securing water, food, and shelter. He possesses a survival knife, a machete, bear spray, and a homemade self-defense weapon.
While navigating the forest, Yamato hears a human cry for help. He discovers a young girl, Lisha, being attacked by large, carnivorous rabbit-like creatures he dubs "Big Rabbits." Despite the inherent danger, Yamato intervenes, dispatching the creatures with his survival knife. Lisha, who speaks fluent Japanese, expresses her gratitude and reveals she is from the village of Urudo. She explains that Urudo is suffering from a severe food shortage and isolation due to the recent conscription of all adult men by a local lord.
Yamato agrees to accompany Lisha to Urudo, offering half of the Big Rabbit he hunted as payment for lodging. Upon arrival, he observes that the village consists only of the elderly and children, who are visibly malnourished. The village chief, Lisha's grandfather, welcomes Yamato, who requests a night's stay in an abandoned house. Yamato, wary of the villagers' intentions, secures his belongings. He notices his physical abilities have significantly enhanced in this new world, with increased strength, speed, and senses.
The next morning, Yamato, with the children's help, begins to address the village's food crisis. He discovers a field of plants resembling rice, which the children call "Inahon" and believe to be poisonous. Yamato, recognizing it as rice, uses it to cook a large pot of stew, which he shares with the hungry children, teaching them the importance of work and self-reliance. He also begins training the children in hunting, using a custom-made crossbow he brought from his world. The children prove to be surprisingly adept at using the crossbow, quickly learning to hunt Big Rabbits.
Yamato learns from Lisha about the "Yamana Tribe," a race of skilled blacksmiths. He visits their forge, seeking to have his crossbow replicated to mass-produce them for the village. The blacksmith, Gaton, a proud and skilled craftsman, agrees to the task in exchange for Yamato's prized survival knife, a unique and advanced weapon from Earth. Gaton is impressed by the crossbow's design and promises to create a prototype within a day.
Yamato continues to lead the children in harvesting Inahon and hunting, while also teaching them basic survival skills and the importance of discipline. He realizes the village's survival depends on his efforts and decides to stay longer than initially planned. He also encounters a giant wild boar, which he defeats with his enhanced abilities, further solidifying his role as a protector. The villagers, initially wary, begin to trust Yamato, and the children, inspired by his strength and teachings, show renewed hope.