Reika Rando serves as the elder daughter in the family of marine farmer and scientist Tatsuya Rando, sharing the position with her twin sister Miki. Her characterization consistently presents a tomboyish personality, deliberately contrasting with Miki's more traditionally feminine and domestic demeanor. This pronounced contrast influenced her French localization name, "Ulrich," due to its masculine connotations.

As part of the treasure-hunting Randou family, Reika actively engages in global expeditions to locate the ancient treasure Quaschika. She pilots the Buncher Hornet vehicles, which form the leg components of the giant robot Acrobunch. Her operational duties involve transforming and combining these vehicles during combat against the subterranean Goblin Society forces.

A key event shaping her background is the Goblin Society's destruction of the family's marine farm, during which her pet dolphin was killed. This event fuels her personal motivation against the antagonists. Throughout their quest, Reika shares the family's living quarters within the Acrobunch robot, which functions as both their mobile base and primary transport.

Her portrayal remains consistent throughout the series' episodes, maintaining her role as a mecha pilot contributing to the family's efforts, her dynamic with her twin sister, and her integration into the family unit's global adventures. Her appearance is confined to the 24-episode television series within the provided materials.