Log Horizon

The online fantasy game Elder Tales is a worldwide phenomenon, immersing millions of players in its intricately conceived virtual world. However, the release of the game's twelfth expansion pack makes that immersion all too literal, as players from around the world are suddenly pulled into the game's no-longer-fictional universe! Now, eight-year ET veteran Shiroe, his friend Naotsugu, the beautiful assassin Akatsuki, and 30,000 other players are faced with the daunting task of learning how to deal with an entirely new reality, one where the Non-Player Characters are actually alive, and the tips and tricks learned while playing with a keyboard no longer apply.
(Source: Sentai Filmworks)