Many years ago, the last remnants of humanity were forced to retreat behind the towering walls of a fortified city to escape the massive, man-eating Titans that roamed the land outside their fortress. Only the heroic members of the Scouting Legion dared to stray beyond the safety of the walls – but even those brave warriors seldom returned alive. Those within the city clung to the illusion of a peaceful existence until the day that dream was shattered, and their slim chance at survival was reduced to one horrifying choice: kill – or be devoured!
In the distant future, mankind has lived quietly and restlessly underground for hundreds of years, subject to earthquakes and cave-ins. Living in one such village are 2 young men: one named Simon who is shy and naïve, and the other named Kamina who believes in the existence of a “surface” world above their heads.
In a world plagued by creatures known as Kaiju, Kafka Hibino aspired to enlist in The Defense Force. He makes a promise to enlist with his childhood friend, Mina Ashiro. Soon, life takes them in separate ways. While employed cleaning up after Kaiju battles, Kafka meets Reno Ichikawa. Reno's determination to join The Defense Force reawakens Kafka's promise to join Mina and protect humanity.
