Nina Klein is a supporting character in Aldnoah.Zero. She is a fifteen-year-old girl who attends Shin-awara High School and is a classmate of Inaho Kaizuka. She is also the best friend of Inko Amifumi. Nina originally comes from the same country as Calm Craftman, a nation that was severely affected by the Heaven's Fall disaster.

Nina is known for her cheerful, gentle, and easygoing personality. She is described as having been well-educated and raised in a good environment, which gives her a flexible and unassuming nature. She enjoys wearing pretty clothes, to the point of exchanging her school uniform for Princess Asseylum's dress on one occasion.

Following the Heaven's Fall incident, Nina moves to New Shinawara along with many of her friends. As the story progresses, she takes on a practical role by working as a helmsperson for ships during rescue missions. Later, she continues this duty as a member of the military, serving as a capable operator in support of the main characters.

Nina's motivations are rooted in her desire to help others and remain close to her friends. Her key relationships include her close bond with Inko, her friendship with Inaho, and her shared background with Calm. She does not undergo a major personal transformation but demonstrates a steady willingness to adapt to the crisis and contribute in a non-combat capacity. Her notable ability is her skill in piloting and navigating ships, which proves valuable for evacuation and supply operations.