Summary
Read Raid manga
Around 50 years ago, after the Korean War, Demon World Gates appeared abruptly all over the world.
Through the Gates, Demon creatures appeared. These otherworldly beings, utterly impervious to modern weaponry, rained destruction across the world.
Just when all hope for humanity was lost, the “Masters” awakened: humanity’s one chance for salvation.
With the appearance of these entities, the world began to change rapidly.