"Fire Punch" is a dark fantasy manga series set in a post-apocalyptic world where humanity struggles to survive in a frozen wasteland caused by an unexplained global ice age. The story centers on Agni, a young man with regenerative abilities granted by the Blessings, supernatural powers bestowed upon certain individuals. Agni and his sister, Luna, live in a small village, enduring harsh conditions and relying on Agni's ability to regrow limbs to provide food for the community. Their lives are upended when Doma, a powerful Blessed with the ability to create inextinguishable flames, attacks the village, believing its inhabitants to be cannibals. Doma's flames engulf Agni, leaving him in perpetual agony as his regeneration prevents him from dying, while Luna perishes in the attack.

Driven by vengeance and an unrelenting will to survive, Agni becomes known as "Fire Punch" due to the flames that constantly consume his body. His journey leads him across the frozen world, where he encounters various factions and individuals, each with their own motivations and struggles. Among them is Judah, a mysterious girl with ties to Doma, who becomes a key figure in Agni's quest. The narrative explores themes of survival, morality, and the human condition, often blurring the lines between hero and villain.

As Agni's journey progresses, he becomes entangled in larger conflicts, including the rise of a religious cult that worships a figure known as the Ice Witch, who is believed to have caused the eternal winter. The story delves into the complexities of faith, power, and identity, with characters frequently questioning their purpose and the nature of their existence. Agni's path is marked by violence, loss, and moments of introspection, as he grapples with his own humanity and the consequences of his actions.

The world of "Fire Punch" is populated by a diverse cast of characters, each with their own Blessings and motivations. These include Togata, a non-binary filmmaker who becomes Agni's companion and mentor, and Sun, a young boy who idolizes Agni but struggles with his own moral dilemmas. The series is notable for its unflinching portrayal of suffering and its exploration of existential themes, often challenging readers to confront uncomfortable truths about human nature. The narrative concludes with a resolution that ties together the fates of its characters while leaving room for interpretation, reflecting the series' overarching themes of perseverance and the search for meaning in a chaotic world.