Two years ago, a mysterious gust of wind swept over the world, taking away everyone's memories without warning. Chaos ensued as people forgot their names and how to communicate, resulting in car crashes, plane accidents, and the breakdown of society. However, a stroke of luck led a young man to a military research facility where he met Johnny, a boy who had undergone experimental memory treatment and still remembered who he was. Identifying as Wataru, the young man absorbed all of Johnny's knowledge before the child's health deteriorated further. Wataru set out to find others who still retained their memories and came across a silver-haired woman named Sophia in San Francisco. Despite Sophia's reluctance to discuss her past, she joined Wataru on a journey to New York, where they discovered the true reason behind the memory loss and the essence of humanity. Along their journey, they learned about civilization's downfall and what it meant to be human.