The story focuses about a young man who is in reality a clone developed by the Japanese army during WW2. Because of some liquids inserted into him, he developed special powers like healing and eternal youth, but will die if he loses too much blood. More than 50 years after the war is over, he is kept along with three other clones in a hibernation chamber. However, the man awakens when one of those clones tries to kill him. Suddenly, two girls appear and take the man home.
Tasogare became a best seller bishōjo game in Japan after its initial release during February 9, and remained a best-seller for several months afterward as well.