Hack//G. U. Vol. 2: Reminisce is the second entry in the . hack//G. U. series containing: Vol. 1: Rebirth, . hack//G. U. Vol. 2: Reminisce and . hack//G. U. Vol. 3: Redemption. As in the previous . hack games, . hack//G. U. simulates a massively multiplayer online role-playing game as the player controls a character who starts playing it. Players assume the role of a participant in a fictional game called The World. While in The World, the player controls the on-screen player character, Haseo, from a third-person person perspective (with optional first-person mode). The player may control the camera using the game controller's right analog stick. Within the fictional game, players explore monster-infested fields and dungeons as well as "Root Towns" that are free of combat. They also can "log-off" from the game and return to a computer desktop interface which includes in-game e-mail, news, and message boards, as well as desktop and background music customization options. In Reminisce, an optional card game called "Crimson VS" becomes available. The player may save the game to a memory card both from the desktop and within The World at a Save Shop. After the player completes the game, a Data Flag appears on the save file, which allows the transfer of all aspects of the player character and party members to the next game in the series. This can also be applied to previous games if the player first finished the Reminsce or Redemption. Players can attack monsters in real time. However, the action pauses whenever the menu is opened in order to select magic to cast, items to use, or skills to perform. The player only directly controls Haseo, while the other characters are controlled by artificial intelligence. The player may either provide guidelines ("Free Will", "Rage", "Life", etc. ) or issue direct commands (for example, to cast a particular magic at a particular enemy) to the computer-controlled characters. Monsters roam the environments freely or guard treasure chests. Once combat is initiated, via a "surprise attack" or the player being spotted, a wall erects around the combat area to prevent escape. Weapons give the player access to the Skill Trigger feature which allows them to perform a powerful attack at the cost of losing SPs. As an adept rogue character, Haseo can wield multiple weapons for close combat. Although Haseo can only use one weapon per battle, during Reminisce the player can change weapons in the middle of Skill Triggers. Under certain conditions, the player may execute an enhanced type of Skill Trigger called "Rengeki". These attacks deal greater damage and fill a Morale gauge, which allows the player and his team members to use a combination attack. Certain plot-related fights, called "Avatar battles", use a different interface which incorporates shoot 'em up gameplay elements. After depleting the opponent's health, players must charge up a "Data Drain" to end the battle. Root Towns are non-combat areas in The World. The player may restock on items, buy equipment, or chat and trade with other "players" of The World. The player may also undertake optional quests and visit guilds. A key feature of all towns is the Chaos Gate. This blue portal is used to travel between towns (called "servers") as well as access the fields and dungeons where battles take place. A password system controls the characteristics of each area. Depending on the characteristics of each word in the three word phrase, the resulting area may have different attributes such as prevalence of monsters or items, among other features.

hack//G. U. takes place in an alternate version of Earth in the year 2017. As depicted in the first . hack game series, the "2nd Network Crisis" was an incident that occurred seven years ago in which many computer systems across Japan malfunctioned. Through the efforts of those games' hero, Kite, the incident resulted in the birth of Aura, the ultimate artificial intelligence (AI), capable of making decisions for itself. Under the guidance of Aura, The World, the most popular massively multiplayer online role-playing game at the time, flourishes and the events of . hack//Legend of the Twilight occur during this four-year period. In late 2014, Aura disappears, resulting in the slow decay of The World and the Internet as a whole. In response, the company that administrates The World, CC Corp, sets up "Project G. U. " and tasks them with remedying the problem. They come up with the "Restore Aura (RA) Plan", in which they attempt to retrieve the fragments of Morganna—an AI that served as Aura's "mother"—and seal them into player characters (PCs) of The World. In theory, this would allow the Project G. U. programmers to manipulate the Morganna program to recreate Aura. Only certain "chosen" players could control these special "Epitaph PCs". After locating candidates to operate the Epitaph PCs, the team proceeds to test the RA Plan despite concerns over "anti-existences" that might damage the Internet. The program fails catastrophically and destroys over 80% of the data for The World. [9] Instead of trying to salvage the data, CC Corp develops The World R:2 and releases it to a new generation of players. However, this new game is less popular than its predecessor and becomes plagued by "player killers" (PKs), players who target other players for fun and sport. The Epitaph PCs which had been lost during the RA Plan disaster resurface in the new version, attached to certain players of interest. Vol. 2: Reminisce: In Reminisce, Haseo and the G. U. staff find themselves trapped inside the game, physically unable to leave or log out, or remove their hardware. Atoli recovers, but is rendered mute, able to communicate only through instant messages. Yata explains that AIDA has copied The World's server, trapping everyone inside to experiment on them. After cracking into the administrative control area, they transfer everyone back to CC Corp's servers. Shortly afterwards, Haseo is approached by Alkaid, concerned for Sirius, a player infected with AIDA. They enter into a tournament to fight Sirius, but Alkaid is ambushed by the AIDA-infected player Bordeaux, who leaves her in a coma. After learning that Sakubo is another Epitaph user, Haseo requests Endrance's assistance for the rest of the tournament. They defeat Sirius and purge him of his AIDA infection that contained Atoli's Epitaph. With Atoli's Epitaph returning, she also recovers. However, her superior from the guild Moon Tree, Sakaki, causes Atoli to slide into a depressed fugue, and be used again by AIDA. Sakaki attacks his own guild, Moon Tree, in order to drive Atoli to the point where she will utilize her Avatar to actively support the AIDA infestation in order to control the real world through the Net, using AIDA as a cat's paw. Haseo liberates Atoli, removing her infection, and driving off Sakaki. Tracking Sakaki, Haseo defeats him after he purposely infects himself with AIDA in a last-ditch effort to gain control of the network. Following this, Ovan appears and reveals that he is Tri-Edge, infected in his left arm with AIDA. The enemy that Haseo believed was Tri-Edge was actually Azure Kite, one of three AIs that Aura had created to destroy the AIDAs.