.hack//Mutation is the second in a four-part game series. It is a single-player RPG that "simulates" an MMORPG (such as for example EverQuest), starring a protagonist named Kite. You can get member addresses of other character and attempt to call them to in game to see if they are on-line to join you in a quest. Like standard MMORPG games, it has many side quests, lots of weapons and armor, a trading system for equipment among other character and the ability to move between different servers. You also have message boards and e-mail to communicate with other "players". The second chapter offers better AI control of other character's, additional items, more characters, access to more servers / areas, and a few other features. Characters from the previous game can be imported, and current characters can be saved for use in future installments.
The story continues after the events of the first game. Kite's friend is still in a coma and he still hasn't found out why. The story deepens as the hacker Helba and the game administrators both start getting involved with Kite. The admins are not happy with him but can use his help to investigate what is going on. The question on what happened to Aura at the end of the first game still gets deeper and new elements concerning the beta version of “The World” (originally called "Fragments") are resurfacing.