Demons' Crest, Vol. 1 (light novel): Reality Erosion (Volume 1) (Demons Crest, Light Novel, 1)

Yuuma Ashihara is playing Actual Magic, a virtual reality MMORPG, when it suddenly begins to fuse with the real world. While he tries to make sense of whats happening, he runs into Sumi, one of his classmates. Before, she was one of the cutest girls in his grade, but shes undergone a terrible metamorphosisinto one of the game's monsters! From the author of Sword Art Online and Accel World comes a story beyond VR and AR, where game and reality are one and the same.