Hydro is one of five space hunters pursuing UMA, an unidentified mysterious creature of high cosmic value. Originating from Stella Water, she wields hydrokinetic abilities that allow her to freely alter her body's shape and properties during combat, primarily controlling water as her weapon.

As the sole female member of her alien hunting team, Hydro maintains a calm, collected, and often cold-hearted demeanor focused on achieving objectives. Her speech carries the distinctive Kyoto dialect. In confrontations, she exhibits intense determination to capture UMA, aligning with her group's goal of securing the associated reward.

Within the narrative, Hydro directly battles Cure Milky, positioning her as an adversary specifically countered by this Pretty Cure member.