Ikuru is a boy who doesn't have long to live. Growing up questioning the purpose of his life and the reason for his impending death, he's constantly confused and lonely. After learning that he doesn't have much time left, he requests that a special "girl" called a AGH-RMS (Artificial Genes Human Regenerated for Mental Support) be given to him. These people are genetically made so that they help heal and ease the mental burdens of the terminally ill.