Whip (ウィップ, Wippu), whose real name is Seirah (セーラ, Sēra), is a character who first appeared in The King of Fighters '99 as the new member to the Ikari team. Her affinity for whips earned her the nickname, Muchiko (ムチ子, Muchiko) -which roughly translates to "Whip Girl" (sometimes translated as "Whippy") - by Ralf Jones. She was planned to enter the series in The King of Fighters '96 but was pushed back to The King of Fighters '99 due to Leona's introduction. According to the developers' diary for KoF 2000, her name Whip is an anagram of Winnie-the-Pooh.
She is a cybernetic clone of K's sister and once worked for NESTS as an assassin. In the 2001 novel written by Akihiko Ureshino, the real Seirah is proclaimed dead and this concept was presumably integrated into the series. She is called Seirah by people who knew her in NESTS though she also responds to the nicknames Sally or Sarah.
She befriended Krizalid under the assumption that he was her brother before she escaped from the cartel. She used Sally as a codename to join the military. She is eventually assigned to Heidern's mercenary unit under her current name, Whip. She enters the King of Fighters tournament to investigate NESTS. While her team isn't present, she privately interrogates NESTS agents to find information regarding herself and the whereabouts of her brother. Once she realizes who he is, she reveals their relation to one another and joins him in his objective to destroy the NESTS cartel. After NESTS's downfall, she returns to her duties under Heidern's command. During the KOF XIII tournament, she serves as backup for the Ikari team and asked Kula Diamond to enter the tournament with K' and Maxima.