Machiko Valencia operates under the callsign Angel Omachi as a core member of Team J9, a mercenary unit combating criminal organizations beyond conventional law enforcement reach throughout the colonized solar system.

She embodies a tomboyish personality and energizes the team as its most optimistic and spirited member, representing the Sanguine element within Team J9's Four-Temperament Ensemble. Her distinctive appearance consistently features red hair and blue eyes.

Her role spearheads piloting and combat operations utilizing Team J9's transforming vehicle and mecha, Braiger. She expertly maneuvers Braiger through its three configurations: the car form Brai-Thunder, the shuttle Brai-Star, and the full combat robot Braiger. She operates alongside teammates Isaac Godonov, Blaster Kid, and Steven Bowie, participating in their coordinated maneuvers, signature tactics, and shared catchphrase during engagements.

Team J9's missions directly oppose criminal syndicates and ambitious power blocs, most notably confronting the Nubia Connection led by Khamen Khamen. This faction's plan to destroy Jupiter for territorial expansion posed an existential threat to Earth, making it a primary focus for Team J9. In some international releases, like the Italian localization, the character retained the name Angel Omachi.

Beyond the original anime series, the character also appears in the *Super Robot Wars* video game series (*Alpha Gaiden*, *GC*, *NEO*), where Team J9 and Braiger are featured units.