.hack//Quantum

Asumi Aida is a cheerful high school student who lives a parallel life inside an online fantasy role-playing game called The World R:X. There her username is Sakuya. While playing together with her classmates Iori Ikuta (username Tobias) and Eri Etou (username Mary) inside the game and having an ordinary treasure hunting adventure, they end up caught in an ominous situation. After an unfortunate encounter with an elite guild and a mysterious player named Hermit, Etou loses consciousness and for an unknown reason is unable to wake up.

Synopsis from Anime News Network