Fire Punch, Vol. 1 by Tatsuki Fujimoto

[Viz] In a frozen dystopia where inhabitants eat flesh to survive, can the destructive powers of fire bring salvation? In the not-too-distant past, the Ice Witch blankets the world in snow, starvation, and madness, leading the inhabitants to seek their salvation in fire. With that, an unusual destiny unfolds for two young orphans, Agni and Luna, blessed with the ability to regenerate. But will this ability prove to be more of a curse than a blessing? Orphaned siblings Agni and Luna, like the Ice Witch who cursed their world, are two of the “blessed,” humans who hold special abilities. However, not all who are blessed are friendly, and after another of their kind attacks Agni and decimates the orphans' village, Agni fights to survive, vowing revenge.