When Tsumugu was younger, he had a friend named Saguri Shinobima. Unable to leave her home due to illness, Saguri lived her life vicariously through "Tsumu's" stories about his adventures. With Saguri wanting to explore the world as well, the two made a promise to go on an adventure when she got better, but she moved away before that dream could come true.

Five years later, Tsumu is pleasantly surprised to learn that he has transferred to the same school that Saguri attends. After Tsumu collides with her, Saguri decides that she wants him to keep his end of the promise they had made in the past. Left with not much of a choice, Tsumu takes Saguri to an abandoned quarry, where big twists await the young adventurers.