The story begins with Kanata Kanbara, a twenty-year-old freeter with no particular aspirations, finding himself in a white, void-like space. There, he encounters Naiarotop, a subordinate god who serves higher gods by creating entertainment. Naiarotop informs Kanata that he has been chosen for a "show" and that his mundane life with no attachments makes him an ideal candidate for an isekai (other world) transfer. Naiarotop explains that he has created a game-like medieval fantasy world called "Lokroa," which has a history of 10,000 years, specifically for entertaining the higher gods by sending humans from Earth to it. These humans are expected to gain "cheat skills" and cause chaos.
Kanata, however, has a beloved cat named Kuromaru, whom he considers family. He refuses to be transferred without saying goodbye to his cat. This defiance enrages Naiarotop, who transforms into a monstrous, plant-like being and throws Kanata into a special location within Lokroa: the "Hell's Hole" (Cocytus), described as a high-difficulty "back dungeon" filled with powerful items and extremely dangerous monsters. Kanata is given only the basic skills of "Lokroa Language" and "Status Check."
Upon arrival, Kanata finds himself in a grim, blood-stained temple-like ruin. He uses "Status Check" to confirm his meager stats. He soon encounters a "Gluttony Mimic," a powerful monster that devours him, severing his arm before he can escape. He then faces a "Predator," another formidable creature that intends to torture him. Just as he is about to be killed, a mysterious white-haired girl with heterochromatic eyes, who identifies herself as a "Lich" named Lunaire, intervenes. She effortlessly defeats the Predator and heals Kanata's injuries using powerful magic.
Lunaire, despite her initial cold demeanor and claim to dislike humans, shows a surprising degree of kindness. She provides Kanata with a "Red Potion" for healing, a "Magic Bag" for storage, and a powerful, though seemingly unusable, ancient sword. She explains that she lives in the "Hell's Hole" because she despises humans who betrayed her. Kanata, realizing the immense danger of his situation and his low level, humbly asks Lunaire for training.
Lunaire, after some hesitation and internal conflict, agrees to train Kanata to reach level 100, believing it's the only way he might survive and leave the dungeon. She provides him with a "Book of Acacia" (a divine-grade item that provides information on monsters and items), a "Necklace of the Magic King's Pursuit" to enhance his magical aptitude, the "Ouroboros Ring" for resurrection, and the "Fool's Magic Sword," a powerful but lightweight weapon. She also creates combat golems for him to train against and promises to accompany him to the surface.
As Kanata begins his training, he learns that the "Hell's Hole" is a place where powerful items are abundant. He also discovers that Lunaire, despite her claims of hating humans, has a surprisingly gentle nature and a fondness for cute things, as evidenced by her creation of a garden and a cat statue. She also possesses immense power, capable of effortlessly defeating high-level monsters. Kanata's journey in the "Hell's Hole" has just begun, with Lunaire as his reluctant mentor, and the path to survival and escape fraught with peril.
