Seifer is an 18-year-old orphan who was born during the Sorceress War and sent to Edea's orphanage. From a young age, he bullied the other orphans, especially Zell. He was enrolled in Balamb Garden where he studied to become a SeeD. Seifer would forget his past in the orphanage due to the memory loss using Guardian Forces causes.

Final Fantasy VIII Ultimania reveals that a famous movie was released about a sorceress who defended her country, and the knight who protected her.[2] Though not directly stated, it is implied the movie inspired Seifer's dream to become a sorceress' knight himself, copying the weapon and battle pose of the actor who played the knight in the film.

At Balamb Garden, Seifer would form the disciplinary committee with his friends Fujin and Raijin, abusing their power to give fellow students punishment and detention. Seifer became a rival to Squall Leonhart, who had also grown up in Edea's orphanage before being enrolled in Balamb Garden, although neither remembers this. Of all the Garden students, only Seifer and Squall chose a gunblade as their specialized weapon.

Even though Seifer had great potential to become a SeeD, his behavior made him fail the exams, and he was labeled a "problem child." Seifer's "romantic dream" is to become a sorceress' knight and he has borrowed books from the Balamb Garden library related to the subject. When he was seventeen, Seifer dated Rinoa Heartilly, a girl working in a resistance group to free the occupied nation of Timber. By the age of eighteen, Seifer is in instructor Quistis Trepe's class but has little respect for his young teacher, and openly defies her.

On the morning of a SeeD exam, Seifer and Squall duel on a rocky field near Balamb Garden and Seifer casts a Fire spell sending Squall to the ground. He strikes at Squall's face, giving him a bloody scar. As Seifer lets his guard down, Squall retaliates, leaving a mirrored scar on Seifer's face.

For the SeeD field examination on that day, Squall and Zell, with Seifer as their leader, form Squad B in the Siege of Dollet. Seifer begrudges having Squall and Zell in his team and declares that the Squad B rule is to follow his command. Unlike the others Seifer does not wear the cadet uniform for the mission, and during the boat trip to Dollet acts indifferent and bored when Xu explains their objective, dissatisfied his squad was not given a more critical task than securing the central square.

Upon entering Dollet, Seifer leads his team to their post on the central square, and upon clearing it of enemy soldiers becomes frustrated with the following idleness. They spy the Galbadians heading to the mountains toward a radio tower, and, acting on impulse, decides to abandon their assigned position, with Squall and Zell following behind. Seifer goes on ahead, leaving Squall and Zell behind when Selphie Tilmitt catches up with them, bearing a message to the squad leader.

Seifer single-handedly clears the radio tower of soldiers before taking the elevator to the top, where the squad finds Biggs and Wedge activating the tower. Selphie delivers the withdrawal order to Seifer, announcing they only have 30 minutes until the boats will leave. Seifer is furious they are ordered to withdraw when there are still enemy forces around but is unwilling to be left behind. He again abandons his team to make his way back to the beach on his own, leaving Squall, Zell and Selphie to fight the X-ATM092 sent to pursue them.

Everyone makes it back to the beach to withdraw in time, and upon arriving in Balamb Harbor, Seifer complains about his squad members' incompetence to Fujin and Raijin who had arrived to greet him. Seifer takes the SeeD Personal Carrier Vehicle back to the Garden, leaving Squall and Zell to walk their way back. The exam results are announced, but because of Seifer's disobedience during the engagement he fails and grudgingly applauds Squall, Zell and Selphie, all of whom pass.

While Seifer is sent to be disciplined for his actions Squall, Zell and Selphie are assigned their first SeeD mission: to aid the resistance faction Forest Owls free the occupied nation of Timber. Rinoa, whom Seifer had introduced to SeeD to hire them, is a member of said faction. Having heard of this mission, Seifer breaks out of the discipline room injuring many in the process, and embarks to assist the Forest Owls by holding the President of Galbadia hostage during a broadcast from the Timber TV Station. Backed into a corner and watched on by Squall, Zell, Selphie, and Quistis—Seifer's former teacher who had been sent to retrieve him—Seifer is saved by Sorceress Edea. Appealing to Seifer's darker side, she convinces him to follow her. Seifer is announced executed by the Galbadian government, and Rinoa reveals her past with Seifer to Squall and his party.

Seifer is believed dead until he shows up in Deling City, standing at Edea's side having become her sorceress' knight. Squall, with their new ally, Galbadia Garden sniper Irvine Kinneas, had been assigned to assassinate the sorceress during her welcoming parade. Despite having been saddened by the news of his death, Rinoa acts indifferent when informed Seifer is alive but that he may soon be killed by Squall. Edea blocks Irvine's shot with a spell and Squall breaks into the sorceress's parade to fight her one-on-one. Seifer stops him, declaring his new status as hero and sorceress' knight. After Seifer's defeat, Squall fights Edea who casts Ice Strike, piercing Squall's shoulder and rendering him unconscious.

When Squall comes to in Galbadia's D-District Prison, he is transported to the torture room by Seifer who interrogates him for the truth about SeeD. Edea wants to know why the SeeD persecute sorceresses, but Squall, who knows SeeD only as a general mercenary force, does not understand the question. While Squall later escapes with his friends, Seifer, now head of the Galbadian Army (formerly headed by Fury Caraway), takes over Galbadia Garden under Edea's orders. Enabling the Garden's mobile functions, he embarks on a search for a girl named Ellone whom his sorceress wishes to find.

Galbadia Garden intercepts a similarly airborne Balamb Garden over the Centra continent near the ruins of Edea's house. With Seifer as commanding officer, Galbadia Garden launches a full assault on Balamb Garden. The Balamb students and SeeDs turn the battle and infiltrate Galbadia Garden. Squall and his party confront Seifer, who is defeated and left unconscious and disgraced on the floor.

Squall's party defeats Edea who relinquishes her sorceress power to Rinoa, who, being possessed, revives Seifer and orders him to raise the Lunatic Pandora. During the entire ordeal Edea had been possessed by a sorceress from the future, Ultimecia, but it is unknown at what point Seifer learned of this. Edea is no longer a sorceress, yet Seifer continues to follow Ultimecia's orders, and the G-Forces follow his lead. Ultimecia wishes to destroy the world via time compression, but it is unknown if Seifer knows of her actual goals.

Under Ultimecia's orders, Seifer has the G-Forces resurrect the Esthar weapon Lunatic Pandora from the depths of the ocean. Restoring the device to active status he directs the pillar to be placed upon Tears' Point, precipitating the Lunar Cry that decimates Esthar City and brings Sorceress Adel's tomb down from the orbit to be a new host for Ultimecia. G-Forces recover Ellone from the Lunar Base escape pod crash site, and Seifer holds her hostage inside the Pandora for Ultimecia's use while waiting for Adel to recover.

Squall and his party invade the construct with an Estharian airship. The toils have taken their toll on Seifer, as his hair is unkempt and his coat is blackened and falling apart. As the G-Forces begin to question their loyalty to Seifer, Fujin, and Raijin, who up until now had followed him loyally, beg him to stop, and release Ellone.

Seifer claims it is too late to go back and wishes them a good life as Fujin and Raijin depart and leave him to his own devices. Squall asks if he's still going to continue "with this knight thing" to which Seifer replies he's retired and now considers himself a young revolutionary, saying he's going to make it to the goal since he's come so far with no interest in sharing it with Squall. The two engage in battle, and if Squall has obtained Odin, Seifer bisects him when he is summoned and Gilgamesh takes his place, knocking Seifer down.

Despite his defeat, Seifer captures Rinoa and offers her to Ultimecia in the body of her new host, Sorceress Adel. Seifer flees the scene as Squall's party intervenes. After Squall's group defeats Ultimecia within Adel's body, Ellone helps Ultimecia cast time compression allowing Squall to reach her era and beat her. Seifer returns to Balamb Town with Fujin and Raijin where they spend a day fishing together. Raijin catches a fish, and Seifer throws down his fishing rod in frustration, but Fujin kicks Raijin into the sea. Seifer laughs before looking up at the passing Balamb Garden with a smile on his face, implying he has put his hatred of them to rest and moved on.

