Genshoku no Kotou

A man washed up on an unknown, isolated island has lost his memory. Giant creatures roam around, ruthlessly devouring their prey. Suddenly, the man trembles in fear and discovers an extremely high castle wall. He expected to see signs of civilization and humans, but a large number of corpses were dumped from the top of the castle wall, refusing to come. As the man secretly watched the situation on the castle wall, he began to feel a strong desire to go to the other side of the wall. What will happen on the other side of this high wall, and what will be the fate of this man? Source: MU