The story begins with Kai, a 13-year-old boy from the impoverished village of Rag, fighting a brutal battle against the ape-like Gray Ape tribe in the "Hento" region. Human races, like Kai's people, are physically weaker than demi-humans and rely on coordinated group tactics, specifically spear formations, to survive. Kai, positioned in the middle of his squad, targets the legs of an enemy warrior. Despite the chaos and the loss of two comrades, Kai manages to wound the Gray Ape with his spear and then finishes it off with a knife to the throat. The battle is fierce, and Kai is thrown back by the enemy's wild swings, losing consciousness as he contemplates his hunger and the grim reality of his life as a disposable soldier.
The narrative then shifts to the dire state of the human race, facing existential threats from demi-human tribes who are encroaching on their lands. Kai, unaware of national crises, only understands the immediate struggle for survival. He recalls the village elder's teachings about reincarnation and the possibility of a new life in a different world after death. His thoughts drift to a vague memory of an "onigiri," a food he inexplicably craves. He is jolted back to reality by his comrade, Manso, who informs him that they have won the battle. The arrival of reinforcements from neighboring villages, bearing the crests of various noble houses, turned the tide against the Gray Apes, who retreated. During the battle, a powerful Gray Ape warrior, distinguished by its tiger-striped fur, clashed with Orha, a tall young man with long black hair, who is a "Gokumochi" (blessed with divine power) and a leader of the Rag soldiers. Orha, wielding a massive iron sword, engages in a supernatural duel with the ape, their clash creating shockwaves. Though Orha's sword breaks and the ape escapes, the battle is declared a victory for Rag.
Following the victory, Kai and his fellow soldiers scavenge the fallen Gray Apes for "Shinseki" (divine stones), bone-like objects found within their bodies that contain condensed spiritual power. By consuming the marrow from these stones, they "level up," gaining strength. Kai, having survived, returns to Rag village, a settlement of about a thousand people surrounded by sturdy stone walls for defense, ruled by the local lord, Morok Vezin, known as the "Iron Bull."
Kai, still recovering from his injuries, observes a training session between Vezin and Vasco, the village's strongest soldier. Vezin, a "Gokumochi" himself, demonstrates the power of the blessed, easily overpowering Vasco. Kai, feeling useless and unable to participate in combat due to his injuries, is given some rock strawberries by Manso, who expresses concern about Kai's slow recovery and the village's need for every able body, especially with rumors of Pigmen ("Ogu") causing trouble to the west.
Later, during dinner at the barracks, Kai, now possessing knowledge from a past life, is dismayed by the poor quality of the food and the stark disparity between the soldiers' rations and the lord's table. He also struggles with his newfound understanding of hygiene, leading to a scolding from Manso. Unable to sleep, Kai ventures out to a well and, driven by curiosity and his past-life knowledge, attempts to cast "fire magic." He succeeds, creating a small flame, but is overwhelmed by the drain on his life force. He manages to extinguish the fire with water, but not before being discovered by Jose, Vezin's daughter, known as "White Princess."
Jose, also a "Gokumochi," approaches Kai, intrigued by the glowing water. Kai, trying to hide his magic, is accidentally flipped over by Jose, who possesses surprising strength. The commotion leads to a false alarm of a demi-human night raid, resulting in Kai and other soldiers being punished. Jose, feeling responsible, apologizes and recognizes Kai's potential as an "Emissary," someone with the gift of magic. She warns him about the dangers of magic, especially for ordinary individuals who can easily exhaust their life force. Kai, however, is determined to grow stronger, fueled by his desire for food and a better life. He begins practicing "healing magic" on himself, cautiously experimenting with his limited spiritual power.
Meanwhile, a larger conflict brews as the Pigmen, a formidable demi-human race, attack the western village of Banya. Rag village, despite its recent losses, is ordered to send reinforcements. Kai, still recovering but having secretly practiced healing magic, is included in the contingent led by Orha. The allied forces, numbering around 700, gather to confront the Pigmen. The Pigmen, known for their brutality and tendency to abduct human women, have devastated Banya village.
The allied forces march into a forest, a disadvantageous terrain for their preferred fighting style. They fall into a trap set by the Pigmen, who had fabricated reports of their encampment. The allied army is driven into a swamp, a territory of Lizardmen, who then attack the confused human forces. Orha, acting rashly, charges into the enemy lines, leaving his soldiers vulnerable. Kai, separated from his squad and pursued by a Pigman warrior, is severely wounded. In a desperate act, he uses his fire magic to kill his attacker and then falls off a cliff into a lake.
Miraculously, Kai survives the fall and awakens by the lake. He discovers that his wounds have healed remarkably, and he has gained significant strength, likely from consuming the Pigman's Shinseki. He also realizes he has developed a "Gokumochi" ability, evidenced by the "Kumadori" (markings) appearing on his face. He understands that he has received a "blessing" from an ancient shrine he landed near.
The narrative then returns to the aftermath of the battle, where the allied forces, despite their victory, are in disarray. Banya village is devastated, and the allied leaders convene to discuss the consequences. The Banya village leader is condemned for his deceit, leading to a brutal ritualistic transfer of his "Gokumochi" power to his daughter, who is forced to kill him. Orha, witnessing this, reflects on the harsh realities of leadership.
Back in Rag village, Kai, having been presumed dead, returns to his comrades, who are overjoyed to see him alive. He carries a Pigman's handaxe, a symbol of his newfound strength and survival. The story concludes with Kai's triumphant return, hinting at his future growth and the challenges ahead.
