Personality Biwa Hayahide is an extremely serious, logical, and data-obsessed intellectual. As the "brain" of the famous "BNW" trio, she believes that any race can be won through meticulous preparation, flawless data analysis, and perfect execution. She is stoic and speaks in a very formal and often long-winded manner, breaking down every situation with precise terminology. This can make her seem cold or emotionless, but it stems from her intense focus on achieving a logical, perfect victory. Beneath her analytical exterior, she is an incredibly caring and protective older sister who is deeply devoted to her family and friends.

Appearance Biwa Hayahide has long and incredibly voluminous white hair, which is adorned by a pair of golden embellishments near her fluffy white ears. On her left ear is a simple gold clip, aond on her right is an intricately detailed gold ring. She has yellow eyes, and wears a pair of red under-rim glasses. Her race outfit consists of a fitted dark magenta jacket, adorned with gold buttons, and a pink collar and light pink accent. Her long sleeves have a pink triangular spike pattern on the cuffs. Underneath the jacket is a black button-up blouse with a red ribbon. She wears a dark magenta pleated skirt with a spiked pink design at the top. The skirt has waist cutouts on either side, and there's a red ribbon tied around her waist. Paired with thigh-high stockings with the same pink spikes-one leg featuring a cut-out circle at the top. She wears cool gray heeled loafers with buckles at the top.

• Nickname(s): Victory Investigator
• Birthday: March 10
• Dorm: Ritto
• Height: 171cm
• Three Sizes: B93 / W61 / H88
• Shoe Size: 25cm
• Weight: No change Relationships
• Narita Taishin: A close friend and one of her greatest rivals. As a fellow member of the "BNW, the sharp-tongued and cynical Taishin is a perfect intellectual match for the logical Hayahide. Their friendship is a bond of mutual respect between two serious, no-nonsense competitors.
• Winning Ticket: Her other close friend and rival in the "BNW" trio. The passionate and energetic Winning Ticket is the "heart" of their group, and Hayahide often acts as the calm and logical "brain," grounding her friend's emotional outbursts with data and reason.
• The "BNW" Trio: Together with Narita Taishin and Winning Ticket, she forms the legendary trio of rivals known as "BNW" (representing their names: Biwa, Narita, Winning). Their three-way battle for supremacy defined their entire classic season.
• Narita Brian: Her beloved younger sister. This is the most important relationship in her life. She is incredibly protective and proud of Brian, and she is one of the few who truly understands the quiet girl behind the "monster" persona. She constantly worries about her sister's wellbeing and tries to guide her with logic and care.
• T.M. Opera O: Her roommate. Their dynamic is a fascinating and often comedic clash of personalities. The flamboyant, theatrical, and illogical Opera O is a constant source of baffling data for the hyper-logical and stoic Hayahide. A theorist through and through, she breaks down any problem systemically. Theory-driven as she is, she values practical application, so her methods never end up as just talk. She has honed her ability to compete with the talent of her sister, Narita Brian. She is good friends with schoolmates Narita Taishin and Winning Ticket. (As established earlier) She also tends to be a tad teasing when it's obvious someone likes her. She is great at tidying up, hates the rainy season, She learns everything about the Umamusume she's racing.