The story takes place in the near future. The sea level rises rapidly for unknown reasons, and most of the surface sinks into the sea. The boy Kakuga Natsuo, who lost a leg in an accident when he was a child, is tired of city life and moves to a rural town by the sea. His grandmother, who was once a marine geologist, left him only ships, submarines and a pile of debts. In order to retrieve the "lost future", Natsuo, together with the mysterious debt collector Catherine, dives into the sea to the underwater warehouse where his grandmother's legacy is said to be kept. There, he meets an incredible girl "Atori" who is sleeping in a coffin-like device. She is a robot with a structure that is so precise that it is indistinguishable from a human being, and she has rich emotions. Atori, who was salvaged from the seabed, said: "I want to complete the last order left to me by my master. Before that, I will become Mr. Natsuo's legs!" In a peaceful town that is gradually sinking into the sea, the unforgettable summer of the boy and the robot girl begins. Adapted from the game of the same name "ATRI -My Dear Moments-" published by Front Wing × Pillow, it was recently announced that it will be adapted into an animation