One year ago, Yuuta lost his father from a car accident. Now in the 6th grade, Yuuta goes to catch a beetle at a dam on a deep mountain. Yuuta often went there with his father. There, Yuuta meets a strange old man. Due to heavy rain, Yuuta slips and falls down a bridge. He becomes unconscious.
When Yuuta awakes, he see a child Saeko in front of him. Saeko takes Yuuta to a village that looks like something that existed 30 years ago. Yuuta has the feeling that he went into the past. He also meets Kenzou, who is the same age as Yuuta. They promise to go catch a bug the following day. Saeko then takes Yuuta to an old house. An old woman there treats Yuuta like a cousin. Yuuta doesn't know what is going on. At night, the strange old man he met earlier appears and tells Yuuta that he will belong to this time period for a month. Precious summer vacation for Yuuta begins ...