This paper doll is the Rumia, based on the game series Touhou Project, the paper model was created by Dark Knight. There is another Rumia in chibi form here: Touhou Project Papercraft – Rumia. Rumia is a weaker youkaithat can manipulate the darkness, but judging from her Embodiment of Scarlet Devil appearance, she is only powerful enough to make it seem like late evening. Apparently she is quite simple-minded, but isn't featured in enough conversations for details about her personality to be revealed.
Rumia's hair ribbon is actually an amulet. She can't touch it, so she can't take it off. In the events of Embodiment of Scarlet Devil, she's attacked by the heroines for no reason, and has nothing to do with the main story.
According to comments about her in the Bunbunmaru Newspaper and in Perfect Memento it seems that she's constantly surrounded by a mass/blob of darkness at all times except during the new moon, and so is rarely actually seen in person. Despite her innocent appearance, she eats humans.
Rumia has the ability of manipulating darkness. By covering herself in pure darkness, she is able to prevent sunlight from passing thought the darkness as this darkness is magical in nature, and can render traditional lights such as torches useless within it. Because of this, people who happen to go inside the darkness would not able to see anything, but it looks like even Rumia also cannot see, as she might crash into trees while flying.
The apprearance of the darkness outside its reigon looks like a spherical circle that is moving. Rumia says "I'm fine in moonlight," meaning she doesn't need such ability on the night of a new moon. Also, the names of Rumia's spell cards are also related to darkness.
You can download this Touhou Project paper model here: Touhou Project - Rumia Free Doll Papercraft Download [mediafire]