Demon Control Front

This is a story about "revival of spiritual energy". [Demons] invaded human territory in 2076 AD. No one knows where they came from, and humans' current weapons cannot cause any harm to them, so they don't know how to fight against them. Therefore, human civilization has suffered an unprecedented crisis. In less than three years, the number of humans has only reduced to two-fifths of its original number. Until, one day in 2080 AD, humans and [gods] entered into a contract. Therefore, human beings gained the power to fight [demon] and opened the "Era of Demon Control"...