Seth/Story

The King of Fighters 2000
Seth was ordered by his superior Ling to enter the King of Fighters tournament in order to capture the Hizoku leader, Ron. To do this, he searches for answers in China. During his search, he was ambushed by Lin, another Hizoku member searching for Ron. During a quick fight, Seth tells Lin everything about the Hizoku, which greatly surprises him. In order to capture Ron, Lin decides to team up with Seth for the upcoming 2000 tournament. The two travel to Japan to meet up with Benimaru Nikaido and Shingo Yabuki; the former knowing Seth.

After surviving the Zero Cannon's second shot during the tournament's climax, Ron appears before the Benimaru Team. Seth learns that Ling is really Zero in disguise and that Ron had joined with NESTS.

The King of Fighters 2001
Prior to the the 2001 tournament, he somehow tracked down Iori Yagami and convinced him to join this year's KOF with Vanessa and Ramón to take down the NESTS cartel, with him convincing Iori after telling him that Kyo Kusanagi would be there. During the team's ending, the three attempts to arrest Iori for further questioning, with Iori preparing to fight them with an unknown outcome.

The King of Fighters XI
Seth would continue to investigate Ron's whereabouts and activities, presumably to prevent him from becoming too powerful. While he did not participate in the eleventh tournament, he was invited to attend Heidern's conference with the Agent Team.

The King of Fighters XIII
Although Seth did not participate in the thirteenth tournament, the Story Mode reveals that he, along with Ramón, Vanessa, and Blue Mary were hired by Heidern to work behind the scenes to investigate the tournament, as well as Those from the Past. During their investigation, they discovered one of the Time Stones.

After Ash Crimson erased himself and Saiki from history, all memories of him were erased from all who knew him, including Ramón.

KOF: Maximum Impact
Seth's life in this timeline is exactly the same as his mainline counterpart up until The King of Fighters 2003.

In the Maximum Impact series, he is often blamed for causing Fate's death. Seth gave him information about Duke at Fate's request, which eventually motivated the latter to stand against the crime lord. In Alba and Soiree's eyes, the agent gave Fate false information and set him up for his death. Although they learn the truth behind their adopted father's death later on, the Meira brothers often target Seth as an act of vengeance.