Twenty years after a global catastrophe plunged Earth into the "Apocalypse," transforming civilization into ruins and unleashing mutated "Monsters," a 16-year-old high school student named Kato Hyogo awakens in a derelict apartment in what was once Okayama. With no memory of the past decade and a half, he is immediately thrust into a terrifying new reality, narrowly escaping a giant black panther-like "Black Panther" and a rock-armored "Rock Crusher Dragon."
He is rescued by Saeki Mikuma, a stern, muscular man in his early forties, a master of the "Ouka-ryu Kenjutsu" sword style and former riot police, and his young companion, Shimada Masaru, a capable "Apocalypse Kid" who uses homemade grenades. Saeki explains the "Apocalypse," the emergence of "Monsters" (which drop "crystals" as currency), and the existence of "Awakened" individuals like Kato, who appear suddenly with lost memories and unique abilities. During a goblin ambush, Kato, a former Kendo club member, instinctively uses his skills and a grenade to help them escape, beginning his reluctant adaptation to combat.
The trio reaches "Kusano Town," a fortified settlement with strict laws. Saeki, a pragmatic survivor, informs Kato that he will be left behind, as his mission doesn't allow for dependents. Kato, initially panicked and feeling abandoned, resolves to become self-reliant. He attempts to sell a pack of cigarettes (a rare luxury) to acquire supplies, but, unfamiliar with the world's "crystal" currency, is scammed into accepting worthless paper money for a "Traveler's Set" and a wooden sword. Despite this setback, Kato, driven by a desire to repay his debt and a fear of being alone, insists on joining Saeki and Shimada. Saeki, recognizing Kato's potential as an "Awakened" (though Kato's "Point Armor" ability remains unknown to him), reluctantly agrees, emphasizing that Kato is now responsible for himself.
As they journey, avoiding bandit-infested main roads, Kato faces various monsters, from the acid-secreting "Rotten Fruit" plant that nearly consumes him, to fire-breathing "Great Lizards" and thieving "Steel Monkeys" that steal his worthless cash. He gradually hones his combat skills with the wooden sword, learning to hunt and extract crystals.
Meanwhile, a mysterious, black-cloaked man named Mauro, with red hair and heterochromia, conducts an experiment. He injects a wounded goblin with a strange red liquid, transforming it into a monstrously powerful "Hobgoblin." This new creature brutally annihilates an experienced group of four adventurers (Long-haired man, Kuramoto, Shimizu, and Kaneda) who were hunting a Great Lizard, devouring their bodies to heal its own wounds. Mauro, observing from afar, expresses interest in Kato, hinting at a deeper connection or future conflict. Kato, sleeping in Kusano Town, senses a disturbance but dismisses it as a dream.
The chapter arc sees Kato transform from a helpless, naive high schooler into a determined, albeit still clumsy, survivor actively participating in the harsh realities of the post-apocalyptic world. The brutal introduction of the Hobgoblin marks a significant turning point, escalating the threat from natural monsters to engineered, intelligent, and far more dangerous foes, setting the stage for future challenges.
