(Touhou 11, 12.5) Has wavy, grey-greenish, short hair and dark green eyes, wears a black hat with a yellow ribbon around it. A closed, dark blue "third eye" is positioned over her heart, with cords wrapped around her torso and attached to each of her ankles. Wears a yellow shirt with diamond-like blue buttons and dark green collar. The skirt is also green with a faint flowery pattern, but a lot lighter. Her socks are black.
(Touhou 13.5) Same as above, except her hair is bright green with yellow shine and it is slightly shorter. Her third eye and its cords are now dark purple and her socks are dark blue.
Koishi Komeiji is Satori Komeiji's younger sister. She wanted to avoid the hate and dislike which Satori experienced due to her mindreading abilities, so she sealed away her own Third Eye. This backfired, since she gained the ability to read and manipulate people's subconscious, an even greater ability. However, she also became much more carefree as a result, and didn't mind as much.
She now spends much of her time wandering the world aimlessly. After her encounter with the heroine in Subterranean Animism's Extra Stage, however, she became curious, and wanted to start actually meeting people.