Bright smoke cold fire

"When the mysterious fog of the Ruining crept over the world, the living died and the dead rose. Only the walled city of Viyara was left untouched. The heirs of the city's most powerful-and warring-families, Mahyanai Romeo and Juliet Catresou, share a love deeper than duty, honor, even life itself. But the magic laid on the Juliet at birth compels her to punish the enemies of her clan-and Romeo has just killed her cousin Tybalt. Which means he must die"--Amazon.com.