The story begins with Kirie Minaret, a sixteen-year-old village girl, being unexpectedly chosen as the new Hero. This revelation comes on her birthday from a castle official, informing her that the power of the previous Hero, who died in battle against the demon army, has been inherited by her. Kirie, aware of the kingdom's aggressive expansionist wars and the Hero's role as a disposable weapon, feels a sense of dread, knowing her likely fate. She is taken to the castle in a luxurious carriage, leaving behind her tearful mother and sister.
Upon arrival, Kirie is dressed in fine clothes and brought to the audience chamber for a Gift assessment. She is guided to the throne where King Burtogu, a formidable conqueror known as a tyrant, awaits. He is accompanied by his minister, Gustav, a portly, mild-mannered man, and a mysterious woman named Judas, who carries a crystal ball and is implied to be a oracle. After Kirie introduces herself, Judas uses the crystal ball to diagnose Kirie's Gift. To everyone's surprise and disappointment, Kirie's Gift is revealed to be "Boiling." This seemingly weak ability causes immediate skepticism and mockery among the nobles.
The King, unimpressed, orders Kirie to the knightly training grounds for a practical demonstration. There, with a sword in hand, Kirie struggles to activate her Gift. Guided by a gruff knight, she eventually manages to boil the water in a cup she was given, confirming her Gift is indeed the ability to heat water. The nobles' amusement turns to scorn, and Kirie is deemed a "Boiling Hero." The next day, the King, seeing no military value in her, grants Kirie permission to return to her village, a decision she welcomes as it means avoiding the front lines.
However, the King and Minister Gustav have a sinister plan. Gustav confronts the King, questioning why Kirie was allowed to leave alive, as a Hero's death is necessary for a new one to emerge. The King, prioritizing the kingdom's reputation and avoiding internal unrest, reveals his true intention: to have Kirie's village attacked by bandits and annihilated, thus eliminating her without direct royal involvement and ensuring a new Hero would eventually be born.
Kirie returns to her village, Rib, and is joyfully reunited with her best friend, Alka, and her mother and younger sister, Claire. The reunion is heartwarming, filled with familiar comfort and love. However, that night, her peaceful life is shattered. An intruder enters her room and attacks her. In a surge of adrenaline, Kirie manages to disarm and kill the attacker. Her relief is short-lived as she discovers her mother and Claire brutally murdered. The house is set ablaze, confirming this was no random act of violence but a targeted massacre.
Realizing the attack was not by common bandits, Kirie, fueled by grief and rage, escapes the burning house with a sword. She encounters the attackers, led by a man named Caron, who reveal they were ordered to kill her and her village. Kirie uses her Gift, now amplified by the deaths she has caused, to trigger an avalanche, killing four of Caron's men. She then confronts Caron, torturing him to extract information about the orders. Caron reveals that the attack was ordered by the King to ensure a new Hero would emerge after Kirie's death, and that the village's destruction was a cover. He also provides information about Caron Styx, a Major General.
Kirie, now a vengeful warrior, travels to the capital city, Dite, disguised and seeking Caron Styx. She encounters Joanna, a member of an anti-establishment resistance group. Joanna, whose group was informed by Kirie's dying friend Kenny, proposes an alliance. Kirie, driven by revenge, agrees, seeing the resistance as a means to achieve her goals. They infiltrate Caron Styx's mansion, where Kirie confronts and brutally kills him using her boiling ability.
During their escape, they encounter a young, silver-haired girl named Beat who is being held captive. Kirie, despite her reluctance to form attachments, feels compelled to save her. Beat, it turns out, possesses healing magic and is revealed to be a former slave of Caron Styx. The resistance, led by Balji Ritainer, offers them refuge in their hidden base beneath a weapon shop. Kirie, still grappling with her trauma and the loss of her family, finds herself increasingly protective of Beat, who also seems to have a strange attachment to her. The story ends with Kirie resolving to confront the King, her ultimate target.
