Rainbow Fireflies (2012)

Original title: 虹色ほたる 〜永遠の夏休み〜

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