A university student, Kishimori Hiroto enrolls in an education internship as a teacher in a middle school of a countryside harbor town, Seitenchou. On the way to his temporary residence, a replis - an artificial being constructed to help humans -with the name of "Reu" appears lying in the middle of the road. After a variety of circumstances, Reu is put under the care of Kishimori until her master is found. That is, until a mysterious organization appears...