The Lost Child is a sci-fi RPG that follows the story of an 11-year-old girl named Konpei who has been searching for her older sister, Chihaya, for years. She receives a mysterious package with a strange device inside, which leads her to an underground facility where she discovers that Chihaya may still be alive.
The gameplay in The Lost Child is divided into two main parts: exploration and combat. Konpei can explore the various areas of the facility, interact with other characters, and solve puzzles to progress through the story. When enemies appear, Konpei must use her device to attack and defend herself in turn-based battles.