...
Girl: (I don't know what he's saying, but he seems friendly.)
The titular focus of the game Deemo. A thin, silhouette-like humanoid that accompanies the Girl in the world she falls into. They work to discover and play songs on a piano sprouting out of it, in the hopes of making it grow large enough to allow the Girl to climb back through the window she came from.
Is later revealed to be the mental manifestation of Hans, the Girl's older brother and an expert pianist who died saving her life in a traffic accident.