Green Flames (Prince of Tennis Fan Fiction)

At the culture festival, the mysterious girl Shin shows up. In a tennis booth, she shows her abilities in tennis, but just after that, she disappears. But for some reason, the sight of her eyes remains in their memories. Three years later, she shows up again when the team has moved to the high school division of Seishun Academy. Who is this mysterious Shin, and what's the secret behind those memorable eyes of hers?