Mobius. An idyllic world that exists for the sake of letting people forget about the pain and problems of reality. In this world created by a sentient vocaloid program, μ (Mu), reality and fantasy has become blurred, allowing people to relive their high school years in bliss.
Yet in this seemingly beautiful and perfect world, something is amiss. The choice to remain in the fantasy or escape to reality is yours in The Caligula Effect: Overdose!