Coopa, a ten-year-old girl, serves as Melt's assistant, bringing an enthusiastic personality and significant domestic skills to the role. Her primary duty involves cooking nutritional meals for the party, expertly prepared from rations and monster meat; she only discloses ingredients if questioned. Despite her youth and non-combat focus, Coopa displays remarkable physical strength, effortlessly carrying Melt's heavy rods and even piggybacking an injured adult. In battles, she functions as Melt's caddy, handing him required rods while frequently correcting his selection errors. She also crafts explosives, particularly smoke bombs essential for group escapes. Coopa speaks with consistent politeness, using honorific suffixes for others.

Her unwavering loyalty to Melt stems from generations of family service to his lineage. This devotion persists despite frequent clashes, including an argument where Melt fired her. Coopa actively attempts to refine Melt's manners into gentlemanly behavior. Her narrative begins when Jil's party rescues her from a slime, leading her to introduce them to Melt; both then join the group.

During "The Sword of Uruk" timeline, Coopa becomes Melt's secretary at his resort, unaware it facilitates a Ponzi scheme. By episode 7, she and Melt travel with the Golden Knights before rejoining Jil's party to pursue Neeba and Kaaya after their betrayal. The epilogue shows her serving Kaaya alongside Melt as a retainer.