The Extra Stage boss Komeiji Koishi's theme, "Hartmann's Youkai Girl", is likely named after psychologists Eduard von Hartmann, whose magnum opus, "Philosophy of the Unconscious", may have very well inspired Koishi's ability to manipulate peoples' subconscious, or Heinz Hartmann, whose work on ego psychology shows up in the names of Koishi's spell cards.

The theme is constructed in a way to sound remarkably similar when played in reverse, possibly to further her psychology-driven inspiration. In music, this is often referred to as a "musical palindrome".