The last time Momo saw her father they had a fight, and now all she has left to remember him by is an incomplete letter that he had started to write her, a blank piece of paper penned with the words "Dear Momo," but nothing more. Moving with her mother from bustling Tokyo to the remote Japanese island of Shio, she soon discovers three goblins living in her attic, a trio of mischievous spirit creatures who have been assigned to watch over her.