Esta was a member of the Big Horn Tribe who gave birth to a son, Ryu. When tribal leaders declared Ryu's white skin a curse and ordered him sacrificed to the Tyrannosaurus Tyranno, Esta was forced to abandon her infant son. She pleaded desperately with the tribe's shaman to spare Ryu, but her pleas were ignored.

Driven by unwavering belief that Ryu lived despite the tribe's certainty of his death, Esta left her people to search for him. She dismissed others' claims that her quest was hopeless, sustained by persistent dreams where she saw Ryu as a grown man. Esta refused to accept his death and continued her search for years.

Upon finally reuniting with her adult son, Esta recognized him instantly. She collapsed into tears, embracing Ryu and explaining her forced abandonment. Ryu comforted her, expressing joy at their reunion.

In the series finale, Taka took Esta hostage, using her to lure Ryu into a confrontation as part of his vendetta. Taka threatened her life, but Esta survived this ordeal. After the conflict's resolution, she joined Ryu, Ran, and Don on their continuing journeys.

Physically, Esta possessed dark skin and dark hair, a stark contrast to Ryu's appearance. Though she bore no resemblance to her son, her recurring dreams of him as an adult enabled her immediate recognition when they met.