Scarlet and Komeiji Breakdown

Flandre Scarlet and Koishi Komeiji
Flandre has been depicted in some fan-art alongside Koishi. This could stem from the fact that they both are extra stage bosses and possess destructive powers greater than those of their sisters, and that they (Satori and Remilia) both own mansions, Remilia the Scarlet Devil Mansion and Satori the Earth Spirit Palace. Not only that, but Flandre and Koishi have spent most of their lives in their sisters' mansions.

Koishi is occasionally drawn with some sort of connection to Flandre Scarlet, since both are extra-bosses who are the younger sisters of the owner of a mansion from the same game.

Other Facts (Similarities and Differences)
Similarities:

Differences:
 * Flandre and Koishi both appear in the game Touhou Sky Arena.
 * The extra stage bosses have fantastic boss themes:  U.N. Owen was Her  and   Hartmann's Youkai Girl .
 * They are my favorite characters.
 * They resemble to their elder sisters.
 * They both appear in the doujin game Touhou Soccer (2).
 * Flandre's birthday is known; Koishi's is unknown.
 * Flandre is about 495 years old; Koishi's age is unknown.
 * Koishi is a Satori (Youkai); Flandre is a Vampire.
 * Koishi now spends much of her time wandering the world aimlessly; Flandre spends her time locked up in the basement due to her destructive powers.
 * Flandre appears in the doujin game Touhou Koubutou (locked character; to unlock her, you have to play story mode with Reimu, Marisa and Remilia,  no continues ), Koishi doesn't.