Zack Fair is one of the main protagonists of the Compilation of Final Fantasy VII. Originally a minor character that appeared only in flashbacks, Zack is the main focus of Crisis Core, exploring his story which leads into Cloud's story of the original Final Fantasy VII.
Zack is introduced as a SOLDIER 2nd Class during a virtual training session with his mentor Angeal Hewley, the original owner of the Buster Sword. Shortly after,Kunsel informs Zack that one of the SOLDIER 1sts has left Shinra and taken some of the 2nds and 3rds with him. During a meeting with Director Lazard where Zack and Angeal are to be sent to Wutai, Zack learns that Genesis is the missing 1st. Angeal also tells Zack that he has recommended him for 1st Class. After Zack shows off his skills in Wutai for the director, they encounter strange soldiers that Sephiroth identifies as Genesis copies. Upon realizing that Angeal has gone missing, Sephiroth concludes that he, too, has abandoned Shinra. Even though Sephiroth is his hero, Zack denies his notion, claiming that Angeal would never abandon them.
Later, Zack is sent with Tseng of the Turks to investigate Genesis and Angeal's hometown of Banora. There, Zack meets Angeal's mother, Gillian, who reveals the history of the Buster Sword. After fighting through a secret facility and meeting Genesis, Zack returns to the village to find Gillian dead and Angeal holding his sword over her.
Angry and confused, Zack pushes him out the door, but is interrupted by Genesis who compares SOLDIERs to monsters and reveals his single black wing. Genesis flies away and Zack can only watch as Banora gets bombed.
Upon Zack's return to Shinra HQ, Lazard promotes him to 1st Class and gives him an assignment with Sephiroth. However, their meeting is interrupted when Genesis' army swarms Midgar, sending both heroes to defend the city. During his sweep of Sector 8, Zack meets Cissnei, a young Turk that wields a shuriken. When he tries to help her, however, he is stopped by Reno and Rude. After he successfully defeats the Genesis copies, Cissnei poignantly tells him that wings symbolize freedom, not monsters.
Zack and Sephiroth continue their mission to the Sector 5 Reactor where they find Professor Hollander's lab. During investigation, Zack learns a bit about Project G before Hollander happens upon them. Zack chases Hollander throughout the facility, but is stopped by Angeal, who reveals his single white wing and compares himself to a monster. Angeal attempts to get Zack to fight him, but Zack refuses and falls to the slums below.
Zack wakes up in a church and meets Aerith Gainsborough, who he initially believes to be an angel. Zack offers to repay her for saving his life with one date. When he sees the flowers that Aerith is caring for, he suggests that she sell them, filling Midgar with flowers and her wallet with money. . Aerith accompanies Zack through Sector 5 to the market, where he buys her the signature pink ribbon for her hair. Later, the couple travels to the park where Aerith admits that she finds SOLDIER frightening. She's quickly apologetic upon learning that Zack is indeed a member of SOLDIER. After admiring his bright blue eyes, he tells her that they are a mark of SOLDIER and leans in to give her a closer look. She playfully pushes him away and they share a laugh. Zack is then called back to Shinra for another assignment.
During Zack's mission to Modeoheim with Tseng and some infantrymen, the helicopter crashes. While trekking through the snowy hills, Zack meets Cloud Strife, one of the infantrymen who dreams of joining SOLDIER. The two quickly become friends, and Cloud begins to admire Zack.
Inside the abandoned bathhouse at Modeoheim, Zack learns from Hollander and Angeal that Gillian was Project G, resulting in the birth of Angeal. Hollander refers to Angeal as the perfect soldier.
Angeal then fuses with copies of himself to become Angeal Penance, forcing Zack to fight him. Upon his defeat, Angeal passes the Buster Sword on to Zack. Zack returns to Aerith’s church where he is comforted by her after the death of his mentor.
A short time later, Zack changes his hair (to how it is shown in the original game) and encourages Cloud in his attempt to join SOLDIER. He then passes on the words of his mentor to a group of 2nds, who later come to regard him as their own personal hero. Later, Zack helps Aerith build a flower cart and begin selling flowers in the Sector 5 Park. When Aerith tells him that she has twenty-three wishes, he tells her to write them down so he doesn't forget. Zack is then called back to Shinra for another assignment. When he arrives, he finds that he will be working with Cloud once again. Sephiroth then tells them that they are going to Nibelheim, Cloud’s hometown, to investigate the reactor.
When the group arrives, Cloud keeps his helmet on to hide his identity. Zack meets Tifa Lockhart who inquires about the SOLDIER members. She starts to say something else, but runs away instead. The next day, they learn that Tifa is to be their guide to the reactor. At the reactor, Sephiroth insists that Tifa stay outside and orders Cloud to guard her. Inside, Sephiroth and Zack find pods with monsters and a locked room with the sign "Jenova", the same name as Sephiroth's mother. Sephiroth begins to break down, but is interrupted by Genesis who tells him that he is indeed a monster and asks him to join his cause. Sephiroth refuses to help Genesis and returns to the village. After escorting Cloud and Tifa back to the village, Zack finds Sephiroth in the basement of Shinra Manor, pouring over the research papers concerning the Jenova Project. Sephiroth then locks himself in the basement and continues his feverish research.
When Sephiroth finally emerges, he burns Nibelheim and heads to the reactor. Zack follows him and finds Tifa badly injured by his hand. Zack initiates combat with Sephiroth, but is eventually defeated and thrown out onto the stairs. Cloud arrives and takes up the Buster Sword to fight Sephiroth, who falls into the mako pool below. Severely injured, Cloud collapses on the steps near Zack. The two are later taken by Hojo to the Shinra Mansion’s basement, where they are kept as test subjects in Hojo's experiments.
After a vision of Angeal, Zack is able to break free from his tube. He releases Cloud who has become afflicted with mako addiction as a result of the experiments. Here, he replaces Cloud's infantry uniform with that of a SOLDIER 1st Class and fights his way out of Nibelheim.
Coming across Cissnei, she gives Zack a motorcycle to aid his escape. Zack decides to return to Midgar to find Aerith, but is stopped by Genesis, who orders one of his copies to eat Zack's hair. Due to exposure to Jenova cells, however, the copy turns into a monster and Zack is forced to fight. Happening upon Gongaga, Zack once again runs into Genesis and Hollander, who now seek out pure S cells, only possessed by Cloud. Zack, aided by Lazard who has turned into an Angeal copy, defeats Hollander while Genesis escapes. Zack returns to Banora seeking Genesis. When he finds him, he is forced to battle him. After defeating Genesis, Zack carries him back to the surface and joins up with Cloud and Lazard. While enjoying a dumbapple, he notices the Angeal copy that had been protecting Aerith. After it disappears into the Lifestream, Zack finds a letter from Aerith which states that it has been four years since she has seen him and that this will be her 89th and final letter. Zack takes Cloud and heads off for Midgar, leaving behind Genesis who is recovered by two SOLDIER 1sts.
During their travels, Zack and Cloud are stopped by the massive Shinra army. Zack fights valiantly, but is overcome by their sheer numbers and gunned down on the cliff overlooking Midgar. The remaining soldiers leave him and Cloud to die, and Cloud (slightly recovered) crawls to Zack's side. Zack passes on the Buster Sword to Cloud, telling him to continue living for both of them. Upon the moment of his death, Aerith is shown in her church, wearing her signature pink dress, looking up to the sky. (Some fans interpret this as her being aware of Zack's death due to her Cetra abilities, although in FF7 she claims to be unaware of his fate.) As Cloud drags the Buster Sword toward Midgar, Zack is pulled into the Lifestream by Angeal, asking if he has become a hero.