No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. The Steam version is estimated at $657.8K — a different platform, not this one.

The Caligula Effect: Overdose

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. Escape from this false paradise with your fellow students and return to reality in The Caligula Effect: Overdose! Key Features: An Overdose of New Features - The Caligula Effect: Overdose boasts enhanced visuals and gameplay! Explore new scenarios, endings, and the “Forbidden Musician Route” while escaping the virtual world of Mobius. The New Faces of Kishimai High - Play as the newly added female protagonist! Plus, meet two new members of the Go-Home Club, who each have their own new Ostinato Musician to face. Use the Imaginary Chain! - Turn-based battle meets exhilarating action in this refined JRPG battle system! Develop a flawless strategy after using the Imaginary Chain to predict what your enemies will do next! Unite and Escape - Sometimes, it’s hard to go it alone. Befriend over 500 other students in this imaginary paradise to improve your skills in battle and ultimately return to reality.