arcaea is a rhythm game developed by Japanese studio, TypeMo. It was released for the arcades in 2006 and has been available for free online. In this game, the player controls two girls who travel through a broken world, encountering various musical themes and conflicts.

The first is a violinist who encounters a number of musical themes, including classical, rock, jazz, etc. The second is a pianist who encounters a number of musical conflicts, such as the evil spirit, the devil, etc. The girls encounter the music of the past, the remnants of the world they once knew. They begin to notice that the world they once knew is in fact a broken world.