Saigo no hīrō

70 years ago there were 7 protectors. In a world full of demons they were the first line of defense against them. On there last mission they attempt to destroy the largest don't they could imagine. The devil itself. To make a long battle short they exiled the devil by using their souls to create a weapon to banish him. The 70 years following were known as the golden years due to the lack of demon attacks. Suddenly demons start occurring and destroying the country and the cities inside. A teenager receives the soul of one of the protectors and is tasked with finding the other 6 carriers who have the protectors souls inside he has to find the 6 souls in 7 months before the devil returns or face destruction