After the discovery of Keiko's existence. It's best I now explain about who he is. Keiko is the 6th and youngest Anima out of the bunch. His airframe is based off of the F-14D Tomcat. He is equipped for High-Tech Tactical Reconnaissance and Air Defense. He is 12 days younger than Skye when compared to the creation dates. Due his current experimental and prototype development state. he continues to fly with Crimson Squadron's protection, keeping his passive behavior at a high level. His full name is Marble L, Keiko

However, what makes Marble different from the other Anima is that he was created from the Neo-crystal of a crashed Intruder Ace. The crystal possessed unknown power and abilities that were not found in the normal Intruder Types. He was supposed to be called Aerostar by the Intruder Ace Family, and was personally named that by Master, but he had gotten lost and was shot down by EXURO,an RAE prototype fighter, after he accidentally flew into Erusean airspace, while trying to make it back to a lone mothership. The Younger Intruder Ace had died but the crystal remained intact and was found by Asamian Ground Forces. It was taken back into the facility and connected to the last airframe of an F-14D Tomcat. His mental model was constructed. He was expected to have a light grey and white appearance, but when the Mental Model was created and The crystal had become one with the F-14, they turned a glossy Black and Red livery, with the newly born Marble, having an unnatural red eye color. During testing, he had multiple reliability issues, the biggest one being his energy level. If he pushes himself to his limit for long periods of time, his mental waves become unstable, making his aircraft uncontrollable. He will pass out mid flight and won't be able to land. To safeguard this, an A.I was placed in the R.I.O's position for when Marble's power level drops excessively while above 1,000 feet and above, the A.I will take control and land Marble safely. The A.I also helps detect incoming aircraft while Marble does recon. Aircraft development issues were not the only thing holding Marble back from active combat.

Due to this crystal being from one of the Intruder Aces, He was self-aware from his birth and had prior knowledge on how to fly and basic aerial combat. This made it unable to put the knowledge and tactics that the Government wanted him to know. But this also made him a very curious Anima. Before testing, he asks himself "Why do I fly?", "Why do I fight?", "Where did I come from?" ,"Why do humans fight?" ,"Why am I tasked with protecting humanity?", "Whats the point of defending them if they continue to fight?", and "Is there more to life than just combat?". These questions developed Marble dangerously curious and exploratory nature. He does not like being held at the facility and would rather fly and explore. Due to this, Crimson Squadron is tasked with protecting them at all costs. They asked to protect Keiko on their own volition instead of getting paid, and rejected any money offered to them to protect Keiko. According to Crimson F-5E pilot, Ryu Takashi, he said "There is no money in this war-torn universe worth more than raising a lost but curious child."

All this protection was put in place due to Marble's unknown abilities. Marble is unaware but his original program and tech allowed him to be able to launch a worldwide connection to any satellite, Radio receiver, TV station, and Radar on the planet. he can transmit messages and watch multiple areas through screens and cameras. But his most feared ability currently is his capability to launch an E.M.P. While connected to these stations and radars. He can emit Electronic signals that can shut down anything electric instantly. If he were to learn and develop a negative opinion against humanity, he can shut down the entire world single-handedly. He can even take down the Intruders with this E.M.P. Therefore, he is kept in secrecy to other countries of his abilities. This is why i'm only announcing this to all forces of U.N.C.A.F. Don't let his young appearance fool you. Marble is very intelligent and curious, if he develops a bad opinion, he could end the world. Marble is now helping the war against the Intruders aboard the JS Akagi with the other Anima.