In 743, mankind's natural enemy "giant" suddenly appeared in the world. Facing a survival crisis, the remaining humans fled to a place and built three huge walls. At the cost of freedom, people have enjoyed peace in this isolated environment for more than a hundred years... Witnessing their mother being killed by a giant and their father's cruel betrayal. She is determined to join the Survey Corps just to protect the happiness of those around her. "I will live, even though I am alone. I will also make my life full of sunshine. I will protect the love and happiness of others, so that they can live a complete life smoothly, safely and without any worries. Even if I have to pay the price of eternal darkness and bear the price of darkness, I will not be afraid." This decision led her to meet the boy who has been with her for a lifetime...