A Wish (Tsukishima x Yamaguchi

The world was taken over by monsters, to survive the humans hid behind walls and sent soldiers out to fight them of. But with more monsters then humans, they human races started teaching children to become a soldier and now instead of a normal school every kid gets sent to training school where they spend most of there life's training to kill these monsters. Tsukishima the best in the class and most likely survive fighting the monsters has a weakness called yamaguchi.