Saitō, recognized as Bea in English-language materials, commands Stow-on-Side Stadium as Galar's Fighting-type Gym Leader. Her mastery of Galar karate complements a battle demeanor defined by unwavering calm and minimal emotional display—traits forged through strict childhood training that imposed heavy emotional burdens and reportedly erased her smile during formative years. Despite this stoic facade, she occasionally unveils genuine emotions to her partner Pokémon in the heat of combat, hinting at deeper connections beneath her reserve.

Physically, she presents a fit, slender build with tan skin, gray eyes, and a gray bobcut hairstyle. Her signature uniform layers a skintight black bodysuit beneath a modified karate gi: a cut-off white shirt adorned with Fighting-type symbols and Gym Challenge insignia, paired with white shorts marked "193" (interpretable as "ikusa" or "fight" in Japanese). She accessorizes with a black-and-orange glove on her right hand, gray kneepads, a rabbit-eared hairband, and fights barefoot like fellow Fighting specialists.

Her combat philosophy demands confronting stronger foes to spur growth, committing utterly to secure at least a draw even in dire odds—embodied by her mantra: "In order to become strong, one must face opponents who are stronger than oneself." During Gym or Champion Cup matches, strategic prowess defines her approach, though frustration surfaces near defeat, often triggering Gigantamax Machamp and G-Max Chi Strike as a final gambit. Upon losing, she acknowledges sensing her rival’s fighting spirit and admits metaphorical urges to "run away in her bare feet."

Beyond battle, Saitō conceals a pronounced sweet tooth, a trait whose public exposure via fans complicated private indulgence. While smiles remain scarce, they emerge fleetingly around trusted confidants—family, her Pokémon, or certain trainers post-victory—revealing warmth beneath her disciplined exterior.