A little way into the future. Humanity has reached the singularity, and AI technology has advanced dramatically, but human nature itself has not changed at all. The protagonist, Naoto Tanaka, spends his days idly playing games with a girlfriend in virtual reality. However, one day, his mother suddenly dies. From that day on, his everyday life begins to fall apart. But then, before Naoto appears an AI that simulates his mother’s personality...