Fire Punch takes place on an Earth that has become frozen over and barren, purportedly at the hands of a being known as the Ice Witch. The witch is among a few who possess special abilities known as "blessings".

The protagonist, you has the blessing of regeneration, along with your sister Luna. They help the few elders in the village subsist on the meat of your severed arms. One day, their village is visited by a blessed named Doma who offers to take you to his city of Behemdorg. Doma, disgusted at their practice of cannibalism, immolates the inhabitants with his inextinguishable flames. Luna, whose regeneration is slower, also succumbs, but not before imploring you to "live". Constantly on fire, your body breaks down and regenerates, leaving you in anguish. Over eight years, you’re able to control your body again, vowing to get revenge on Doma. You come across a convoy of slaves to Behemdorg and kills the soldiers. A boy named Sun (blessed with the power to generate electricity), who thinks you’re a god, follows you. Later, more soldiers find you, and one of them, Judah, a blessed resembling Luna, beheads you.