Laughter in the End of the World

When corruption consumes the world, the akuma with 101 mouths shall appear. Humanity forgot about their existence, continuing to indulge in sin, until the day when the akuma arrived, and dark descended. Some continued to fight, and after seven days of struggle the akuma was destroyed. Or so they thought. Immortal men marked by the "mouth of the akuma", continue to wander the world. A man bearing the mouth of the akuma, named Godot, has blackmailed a town, extorting food and supplies, and in exchange promises not to harm the inhabitants. One day a man appears, also bearing the mouth of the akuma, accompanied only by a young girl named Haru, whom he calls his sister. Claiming to be an akuma eater, he promises to rid the town of Godot once and for all. Who is this young man, and what are his intentions? How does he plan to kill his fellow immortal, Godot?