world after war

it's a year like no other. after the government opened a door to another world, an alien hybrid race came scrambling through. the war lasted for 20 years from 1980 to 2017 from then on the world's population shrank to a mere 15 million. scattered around the world they all found there way to North America (Canada and the US) where a group was founded to recover the planet. a secret protocol was created to get teens to meet up and hopefully start a life together. the protocol was only made because 60% of the pop is too old to represent the population. the government soon realized that they would be quite a target all gathered together.. because tho the war was over the hybrids still were in Earth.. we just closed the door. the hybrids proceeded to reproduce and grow stronger adapting. so the government created a spec ops group to defend these events. they were known as the Hybrid Exterminators. it consisted of 4 'slayers' and a branch of military specializing in Hybrid control. this story focuses on cal the head hancho of the slayers.