Rapid is a train conductor and an officer on Rebel Army, serving as the head of the Rebel Army's transportation unit. She appears as a villain and playable character in Metal Slug Attack.
Rapid is informed by a soldier that Abigail has ordered her into battle to disrupt the Regular Army's supply lines so she can break their defences as she is the best candidate for the job. Skeptical because she has never fought and that trains aren't supposed to be used as weapons, she follows them anyways. Learning about their supply routes from the soldier, she spots Vita flying about and manages to convince her to help with the mission.
After Vita shoots down the new Regular Army Helicopter, Rapid is surprised and learns that Vita likes to distinguish herself in battle. She tells her that she prefers moderation instead, and offers Vita a ride back to base. Several soldiers also want to board the train, but she tells them to try again next time, much to their disappointment. Back at the Rebel base, Rapid submits several compensation bills to Abigail to cover the cost of the mission.