Yuwakashi Yuusha no Fukushuutan

A Hero is someone chosen by God to receive a supernatural 'gift'. A unique existence, only one Hero can exist at a time, with a new one being chosen upon the former's death. This generation's Hero is an ordinary villager girl named Kyrie whose gift is merely being able to boil water. When her family and friends are slaughtered, Kyrie is backed into a corner and learns the true value of that boiling hot power, and how well it could be used to fan the flames of revenge that burned inside of her.