.Hack//Mutation

.Hack//Mutation is the second of a series of four games, titled .hack//Infection, .hack//Mutation, .hack//Outbreak, and .hack//Quarantine, features a "game within a game"; a fictional massively multiplayer online role-playing game (MMORPG) called The World which does not require the player to connect to the Internet. Players may transfer their characters and data between games in the series. Each game comes with an extra DVD containing an episode of .hack//Liminality, the accompanying original video animation series which details fictional events that occur concurrently with the games.

The games are part of a multimedia franchise called Project .hack which explores the mysterious origins of The World. Set after the events of the anime series .hack//Sign, the games focus on a player named Kite and his quest to discover why some users have become comatose as a result of playing The World. The search evolves into a deeper investigation of The World and its effects on the stability of the Internet.

Kite and BlackRose return to Θ Chosen Hopeless Nothingness but find part of the area locked off. After a quick intervention with Balmung, the two return to Dun Loireag, where Kite is told that his Book of Law he won from the Level Up Campaign has an error that prevents it from being installed, so it is replaced with the Book of Absolute (which also cannot be installed). BlackRose claims to have never heard of the event.

The two receive e-mails telling them to come to Θ Soaring Sky Bounded Abyss if they want to know more about the coma victims. It is actually a trap set up by system administrator Lios. Lios says that they should not pursue the matter any further and proceeds to delete Kite's character data along with the bracelet. Helba, however, interferes, saying that they cannot be deleted because of a mysterious encryption implanted in their character data. She introduces the theory that The World is based on the Epitaph of Twilight, telling the two to look to the Epitaph for clues. She then suggests to Lios to observe the two rather than try to delete them. Lios eventually agrees, deciding to use the two and the unique abilities of the bracelet to investigate the corrupted areas.