Kaito hesitated. The tunnel hummed.
: While you do not age rapidly within the tunnel, the world outside moves on without you, effectively "stealing" your youth if you stay too long. The Mechanism
The story follows a group of high school students, including the protagonist, Taro, who stumble upon the tunnel while exploring the outskirts of town. As they venture through the tunnel, they discover a world that is eerily similar yet disturbingly different from their own.