For the past ten years, Ikuru Yoshizumi has endured a terminal illness, with death looming close. In search of a purpose to sustain him through his remaining days, Ikuru applies to own an AGH-RMS—a genetically modified human with a brief lifespan, created to offer comfort to those nearing the end of their lives. Ikuru is assigned Ai, an AGH-RMS who looks and acts like a girl his own age. Through Ai’s pure love for him, which allows her to cultivate her own personality, Ikuru discovers his own reason to live. As an unavoidable global conflict endangers the future of humanity, Ai and Ikuru hold onto one another for safety and understanding.