The manga's story begins when Isshin Inui invites his friends to go out on a journey on their bikes to find their long lost friend Ayano Hirakawa, who has been gone for years. Their only clue is a last photo that Ayano sent to them from her smartphone before disappearing. Using this clue, Isshin and his friends head up to a mountain. Here, they find the truth of Ayano's fate, and how she ties into a conspiracy of child kidnapping.