The introduction of 7G Network technology was supposed to transform society, but instead threw Japan into chaos. The environment changed drastically, people experienced strange mutations, and everyday life adapted to new circumstances. Agano, a small town, remains one of the few surviving communities, where every adult over 21 has turned into an animal.
Shizuru Chikura, a high school student from Agano, is desperately searching for her friend, Youka Nakatomi. After finding a newspaper clipping showing Youka in Ikebukuro, Shizuru begins getting ready for a trip. With most public transport out of service, she has few options. Fortunately, Tairo Zenjirou, the town’s only human adult and an elderly senpai conductor, helps her learn how to operate an abandoned train.
Resolved to find Youka, Shizuru sets out on her journey. Unexpectedly, on the day she departs, her classmates Nadeshiko Hoshi, Reimi Kuga, and Akira Shinonome decide to join her at the last moment. Together, they embark on a single-track voyage that may bring them face to face with dangers far greater than anything they encountered in Agano.