Chapters 3 through 12 of the light novel detail the protagonist, Sumihara Tsuguto, a second-year high school student, experiencing a bizarre and violent bus accident. Initially, Tsuguto is portrayed as a more passive individual, having learned to avoid conflict to protect his future, a stark contrast to his younger self. This newfound pragmatism is tested when a blonde bully demands his seat on a crowded bus. Tsuguto complies, feeling humiliated as he stands, drawing the attention of other passengers.
Suddenly, the bus lurches violently, its windshield shattering and filling with white. Tsuguto is thrown forward, experiencing the impact in slow motion. He sustains numerous cuts from the glass and a severe blow to his back when he lands, but miraculously, the other passengers appear largely unharmed. Tsuguto, however, finds himself bleeding profusely from his neck, a wound he cannot move his arms to address. As he realizes he is dying, the blonde bully, instead of showing concern, films him with his smartphone, igniting a pure, overwhelming rage in Tsuguto. He glares at the bully, pouring all his hatred and regret into his gaze until his vision fades to white.
Tsuguto awakens in a dark, earthy cave, disoriented and alive. He finds his uniform torn but his body miraculously uninjured. The cave environment is described as vast and natural, with no discernible exit. He encounters a gruff, foreign-looking man mining for stones, who speaks a language Tsuguto inexplicably understands, though he cannot identify it. The man refers to Tsuguto as "tagless" and dismisses him. Tsuguto, observing the man's mining, discovers blue, translucent stones and a clear, colorless stone, which he pockets. He follows the mining path, encountering a fork where other miners are heading. He follows them to a large, open area, a cleared mountain plaza filled with people dressed in medieval-style clothing, suggesting he is no longer in Japan.
He witnesses a system where miners exchange their collected stones for currency at a counter. Tsuguto, realizing his lack of money, sells the blue stones he found for a small amount of currency and a bag. He learns the currency is "Lark" and the blue stones are "magic ore." He also acquires dried meat for sustenance and is directed to an inn called "Dragon's Den Inn." Upon reaching the town, he is struck by the sight of a colossal, thorn-shaped mountain piercing the clouds, confirming his suspicion that he is not on Earth. At the inn, he meets a gruff, giant innkeeper who charges him a significant amount for a room and a "magic stone" for light and heat.
The next morning, Tsuguto, needing to earn money, learns from the innkeeper about "dungeons" where magic ore is mined. He returns to the cave, now referred to as a dungeon, and encounters a young girl with pointed ears and horns, who identifies herself as a "sheep person" and offers to help him find magic ore. She explains the dungeon walls regenerate, but the ore deposits need time to reappear. Working together, they quickly gather a substantial amount of ore. Tsuguto learns the girl's name is "Danaroot" (though this is later revealed to be the name of a group of thugs) and that she is an orphan who works to survive.
Their partnership is interrupted by three thugs, led by Danaroot (the person, not the group), who attempt to extort magic ore from the miners. The girl, despite her small stature, defiantly refuses. Tsuguto, witnessing this, is overcome by a powerful urge to resist, recalling his own humiliating death. He throws a stone at the thugs, provoking their leader, Danaroot. However, the thugs recognize Tsuguto as a "tagless" individual, a designation that instills fear in them. Despite their apprehension, Danaroot attacks. Before he can strike, the sheep-person girl intervenes, shielding Tsuguto and taking a brutal kick from Danaroot. Seeing her injured, Tsuguto's suppressed rage resurfaces, and he confronts Danaroot, who, terrified by Tsuguto's intense gaze, flees with his companions. The girl, injured but conscious, is taken by Tsuguto to a magic item shop, where they pay a large sum for her treatment. They are then forced to leave with very little money, facing the prospect of sleeping outdoors.
