OVA
Description
Nina Wang originated from Artai, surviving as an orphan in underground slums until rescued during a military raid by officer Sergay Wang. He adopted her, assigning their meeting date, September 7th, as her symbolic birthday. This date coincidentally matched the actual birthday of Princess Mashiro Blan de Windbloom, a clue later revealing Nina's true heritage as Windbloom's lost royal heir, supported by the discovery of her cradle in Artai and her genetic ability to wield the Harmonium.

At Garderobe Academy, Nina excelled as the top Coral-class student, driven by a desire to earn Sergay's approval and become Artai's first Otome. Her disciplined, serious demeanor contrasted with Arika Yumemiya's impulsiveness, fostering initial rivalry. Despite this, they formed a tentative friendship with roommate Erstin Ho. Nina harbored deep-seated jealousy toward Arika stemming from Sergay's secret sponsorship of Arika and his past infatuation with Arika's mother, Lena. This jealousy strained their relationship, escalating when Nina discovered Sergay preserved mementos of Lena.

During Schwarz's invasion of Windbloom, Nina witnessed Sergay protect Arika, triggering an emotional collapse. Her intense hatred and jealousy activated the corrupted Ultimate Black Diamond gem, forming a contract with Artai's Duke Nagi. In her enhanced Meister Robe, she attacked Arika, but Erstin sacrificed herself to intercept the blow, dying. This tragedy fueled Nina's vengeful pursuit of Arika, culminating in a destructive battle.

After Windbloom's liberation, Nina retreated with the comatose Sergay to a forest cabin. Upon his amnesiac awakening, she reintroduced herself, implying a desire to redefine their relationship beyond father-daughter dynamics. In the OVA My-Otome Zwei, Nina resided in isolation with Sergay until recruited by Juliet Nao Zhang to explore ancient Artai ruins. There, she discovered the Neptune Emerald gem and was transported to the Black Valley. She forged an interim contract with Mashiro, materializing a new aquatic-themed Meister Robe and wielding a bident weapon. Alongside Arika, she defeated the entity Yuna, demonstrating reconciled cooperation.

The manga adaptation presented an alternate continuity: Nina lacked familial ties to Sergay or Windbloom royalty. Instead, she was an orphan trained as Nagi's Otome. She bonded with "Mashiro" (later revealed as the cross-dressing prince Manshiro), eventually becoming his guardian after Nagi's death. Her primary gem was the Black Smoke Chrysoberyl, and she survived conflicts that fatally wounded allies like Erstin.