.hack//MUTATION Part 2 (.hack//悪性変異 Vol.2 Malignant Mutation – Vol.2?) is the second part in a series of four PlayStation 2 video games based within the .hack universe. The game simulates an MMORPG entitled "The World" and accomplishes this without requiring the player to ever actually venture online. The game is part of a serial storyline, with each of the four games slowly released over the course of a little over a year. .hack//MUTATION's storyline, preceded by .hack//INFECTION, is followed by .hack//OUTBREAK and .hack//QUARANTINE.
Each installment of the game is accompanied by a DVD containing an episode of the .hack//Liminality OVA series. The four episodes happen in the real world, as opposed to the fictional MMORPG, The World, in which the game takes place entirely in. The events of Liminality take place alongside those of the games.