When his parents moved because of work, Yuuichi ended up on a small island in the Pacific. It’s a relaxing place and the school only has around 10 students. One of his classmates is his cousin Nagisa, who he also lives with. However, this tranquil island is shrouded in mystery and there are many traditional rituals and folklore. Yuuichi is excited about such things and one day, he came upon a strange cell phone. But why is there a cell phone here when there is barely radio reception? He meets a girl in front of the sacred tree at the local shrine. She tells him that this cell phone allows him to write messages to his past self and that she wants him to solve the mysteries of this island. [From Hau~ Omochikaeri!]