The final boss, Utsuho Reiuji, is the only final boss of the series whose plan is explicitly to conquer the world, though this is due to her misinterpreting the voice that told her to swallow the Yatagarasu.

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".

The boss of stage 4, Komeiji Satori, uses different spell cards based on which partner the player chose at the beginning of the game. The spell different cards belong to the player's current partner of choice. This turns out to be because of Satori's ability to emulate her opponent's past traumas through hypnosis.