The game contains data for a second party member, despite the fact that Madotsuki is alone in standard gameplay. Using RPG Maker 2003's debugging tools to add this figure to Madotsuki's party shows that it does not have any sprites or even a name. However, various changes occur to the game's world, indicating that Kikiyama most likely used this for testing purposes:

• Almost all Toriningen are despawned; the only exceptions are the one in the Mall who changes the menu's palette when spoken to and the group throwing a party in the wilderness.
• The top-left cupboard in both versions of the Guillotine Room disappears. However, it can still be interacted with: pressing Z or Enter when standing where it normally would be transports Madotsuki to a random cupboard in the Number World, as if she had used one of the randomly generated exit cupboards. Returning to the Guillotine Room restores the top-left cupboard to its normal position.
• Movement is disabled upon waking up.
• The Witch's Flight event can be accessed by walking off the top-right corner of the Mall's rooftop, regardless of whether or not Madotsuki has the Witch effect equipped and active.
• An unused parallax background (named ネオン背景.xyz in the game's files) is enabled in Neon World, which normally has a solid black backdrop in Version 0.10 and all available early builds. This background, which depicts a series of ripples distorting a group of red, blue, and green lights, does not scroll correctly, only showing the top-left corner of it. Notably, this is the only unused background in the final game.

The notion that this invisible party member was used as a debugging tool is further bolstered by the presence of three similar extra party members (which also have no graphics or names) in Version 0.06. In that earlier build, Madotsuki is internally listed as the fourth party member; enabling the first one adds NASU to the game's debug map, though both that version and the one in Madotsuki's room will not progress past the title screen.