After you receive a call from your school doctor she introduces you to a new type of drug that she developed, it apparently triggers certain instincts in a woman that gives them the need to reproduce and getting breed by whoever is close to them during the effect of the drug. The MC (you) now has a lot of power in his hands and can't wait to try it out on the next best girl he can think of. This is a separate game, meaning you don't need to have you're save from the main game to play it.