Kiska, a young man with silver hair, has always been an outcast in his village due to his hair color, which marks him as a descendant of the Arcs family who once betrayed humanity. His only solace was his childhood friend and fiancée, Namia, who loved him despite the village's scorn. His life shatters when three men, led by the village chief's son Darga, murder Namia. Kiska is then falsely accused of the crime, convicted, and banished to the deepest part of the inescapable S-class Katarov Dungeon as punishment.

As a non-adventurer with no skills, Kiska faces certain death from high-level monsters. Just as a demon is about to kill him, a mysterious female voice echoes, "I will save you," and grants him a unique skill called Save and Reset. This power automatically rewinds time to a save point just before his death, allowing him to try again. However, this "blessing" quickly proves to be the beginning of a relentless, brutal cycle.

Within the dungeon, Kiska discovers that the true threats are not just monsters and traps, but beautiful and powerful heroines sealed inside. The first is Ageha Tsubaki, a warrior from another world imprisoned for a century. When Kiska breaks her seal, she becomes obsessively devoted to him. Her love is yandere in nature: if he refuses her advances or shows interest in another woman, she kills him without hesitation, triggering another reset. Other heroines include Judith, a sadistic pure-blood vampire who views humans as playthings and has killed Kiska on sight multiple times, and Kugutsumawashi, a parasitic sword that dreams of becoming human and can control its host like a puppet.

To survive and conquer the dungeon, Kiska must die and repeat events countless times, learning from each death. He develops strategies not to overpower these threats, but to charm them, turning lethal enemies into devoted allies. The narrative follows multiple arcs defined by which heroine's route he pursues. In the Ageha route, her possessiveness leads to the destruction of the world if he chooses another, forcing a reset. The Judith route requires him to withstand her cruelty to earn her twisted affection. The Kugutsumawashi route offers power at a terrible cost. These arcs culminate in a significant narrative turn where Kiska fails so catastrophically that the world ends, sending him back in time 100 years. There, he must change history to forge a path toward a true ending and finally achieve his revenge on those who wronged him. The story, which began as a web novel in 2021 and was later published as a light novel by Kadokawa, remains ongoing as Kiska continues to die and reset in his quest.