Coopa is a ten-year-old girl who serves as the loyal attendant and servant to Melt, a member of a noble but impoverished family from the kingdom of Uruk. Her family has served Melt's family for several generations, which forms the foundation of her deep-seated loyalty and sense of duty toward him. Within the party that climbs the tower, Coopa takes on the essential role of the group's cook, preparing meals from a combination of standard rations and the meat from monsters they encounter. While she does not usually announce the ingredients she uses, she makes no attempt to hide them if asked directly.

Coopa possesses an enthusiastic and cheerful personality, and she is notably polite in her interactions with everyone, addressing others with the respectful suffix sama. Despite her young age and small stature, she demonstrates remarkable physical strength. This is evident when she carries Melt's many rods or, on one occasion, piggybacks an injured Utu, a much larger ally. Her combat role is largely indirect, as she primarily acts as a caddy for Melt, handing him the magical rods he requires during battle. She frequently has to correct her master's mistakes by giving him the correct rod instead of the one he requested. Beyond her support duties, she is skilled in creating explosives and often uses smoke bombs to help the group escape from dangerous situations.

Coopa's relationship with Melt is a central aspect of her character. They constantly clash, in part because she is determined to improve his manners and make him a proper gentleman. Nonetheless, she remains fiercely loyal to him. This loyalty is tested when Melt fires her after an argument, though the nature of their bond ensures they are eventually reunited. In the second season, The Tower of Druaga: The Sword of Uruk, Coopa becomes Melt's secretary at a resort he operates, initially unaware that the business is a front for his Ponzi scheme. She and Melt later travel with the Golden Knights before rejoining Jil's group to pursue the characters Neeba and Kaaya after their betrayal. At the conclusion of the story, Coopa and Melt serve as retainers to Kaaya.

Throughout her journey, Coopa's most notable abilities lie in her domestic and support skills, including cooking, creating explosive devices, and managing her master's equipment. Her hidden physical strength also proves useful on several occasions. While she grows from being merely Melt's servant into a more integral member of the larger adventuring party, her core motivation remains constant: serving and supporting those she is loyal to, particularly her master Melt.