"As a child, Natsuki doesn't fit into her family. Her parents favor her sister, and her best friend is a plush toy hedgehog named Piyyut who has explained to her that he has come from the planet Popinpobopia on a special quest to help her save the Earth. Each summer, Natsuki counts down the days until her family drives into the mountains of Nagano to visit her grandparents in their wooden house in the forest. One summer, her cousin Yuu confides to...