Sounds interesting. Now in High School DxD we have a demon girl with long red hairs named "Rias". Here, we also have some sort of demon girl with long red hair, called "Risara". I notice a trend there
Also, the story says the girl will for a contract with Ryuusuke. "Form a contract with me, and you can become a magical girl!"
Careful with those contracts
Although, the "stabbed and left for dead" bit reminds me much more of Korezon. He could still become a magical girl, wearing a proper magical girl dress and all XD
"No, Ayumu, you mustn't become any cuter!" XD XD XD