We Are One And All - Book One of the Morita Hinako Saga

Morita Hinako isn't your normal young girl. She's as smart as any adult, she thinks. But that doesn't help her when she falls asleep in class one day, and wakes up to find that a classmate has become a monster, and desires to devour her. Her imminent death is forestalled when a mysterious sorceress appears, with the power to change Hinako's life forever. But that won't stop the monsters, human or otherwise, that plague her world and others from trying to kill her for the power that she possesses and barely understands. A dark modern fantasy-horror inspired heavily by Shin Megami Tensei and Persona.