The story begins with the protagonist, a high school student, recounting the devastating accident that left him paralyzed from the waist down. After months of painful rehabilitation and finding solace in video games, he contracts a high fever. While wishing he could escape his reality into a game, he loses consciousness. He awakens to find himself in an unfamiliar, opulent room, and to his astonishment, he can feel his legs and move them. He discovers he has been reborn into the body of Wilm Rosmaria, a character from an action RPG he played extensively. Wilm, a portly noble with golden hair and blue eyes, was a minor antagonist destined to die in a tutorial duel.
Upon realizing his transmigration, the protagonist, now inhabiting Wilm's body, grapples with the reality of his situation. He confirms his regained mobility and the opulent surroundings, which are clearly not his former world. He learns that Wilm had been gravely ill, and his awakening coincided with his recovery. Despite his new body and circumstances, the protagonist is determined to avoid Wilm's predetermined fate. He receives an acceptance letter to an academy, a crucial plot point in the game that leads to Wilm's demise. In a desperate attempt to alter his destiny, he tears up the letter, only for it to reappear, reinforcing the idea of a predetermined fate.
Driven by the need to survive, the protagonist, as Wilm, decides to pursue a path that deviates from the game's script. He learns about the game's magic system, where each character possesses a unique skill, and Wilm's is "Steal." He hypothesizes that he might be able to "steal" magic from others. To this end, he visits a slave market, seeking a powerful magic user. There, he encounters Melsa, a blind snake-like demoness with the "Petrify" magic, who is revealed to be the final boss of a specific game route. Despite her dangerous abilities and the slave trader's warnings, Wilm purchases her, intending to use her power to his advantage.
Wilm's immediate goal is to increase his magic proficiency, particularly his "Steal" ability, to survive his impending death. He learns from a maid that the city is plagued by various criminal organizations, such as the mafia, which are difficult for the local knights to control. This sparks an idea: these criminals, who "sprout" even after being dealt with, are perfect targets for practicing magic. He decides to hunt them down to gain experience and power.
Wilm and Melsa venture into the slums, where they encounter a group of mafia members. Wilm, using his "Steal" magic, incapacitates them by draining their life force. This encounter triggers a flood of memories from the mafia members, revealing their brutal pasts and the city's dangerous underworld. Wilm realizes that Melsa's "Petrify" magic is incredibly potent, and he intends to learn to control it, even if it means stealing it from her. He also learns about the "Black Shadow" mafia, who control the untouchable district.
Later, Wilm and Melsa confront the "Black Shadow" mafia. Wilm's "Steal" magic proves effective against them, but he also gains fragmented memories of their violent actions. He decides to use Melsa's "Petrify" magic to gain experience, removing her blindfold despite her trauma. Melsa unleashes her power, petrifying everyone in sight, including the mafia members and their leader, Diago. Wilm, impressed by Melsa's power and the potential for growth, reaffirms his decision to keep her by his side, believing she is key to his survival. He also learns that the "Black Shadow" mafia are responsible for the plight of the untouchables, including Melsa's younger sister, Arna, who is a key character in the "Demon Lord" route. Wilm offers Melsa a deal: if she helps him, he will help her find her sister.
