Karina is a middle-aged woman with fair, short hair. Like many Eldian women in the camp, she wears a scarf on her head when she goes outside.
Karina has a very kind behavior towards her family members, like her son and niece. She takes pride in their achievements and always supports them, this is seen when she congratulated Reiner on becoming a Warrior and Gabi after hearing what she did during the Marley Mid-East War.
Karina once had a job outside the internment zone. This is how she met a Marleyan man and had an affair with him, leading to the birth of Reiner. Because such unions are forbidden in Marley, she raised her son alone, remaining in the internment zone. Karina eventually revealed his origins to her son, wishing she was born a Marleyan. She ended up convincing Reiner to become a Warrior candidate, so the pair would gain Marley citizenship and Reiner could reunite with his father.
The day of the Warriors' departure to Paradis Island, Karina was in the crowd cheering them, crying. Before he sailed, she expressed her faith in her son and her certainty his father wished him success as well.
At the end of the Marley Mid-East War, Karina and her relatives welcome back Reiner and Gabi to Liberio. Later on, the whole family has dinner. They listen to Gabi's feat and Karina asks Reiner if she could become a Warrior. Hearing his affirmative answer, she expresses joy and pride at the thought of having two Warriors in the family then complains about the Paradis Island inhabitants' existence. As Reiner discusses his time on Paradis Island, she listens before interrupting him and encourages Gabi to stop the inhabitants of Paradis Island.
Karina attends Willy Tybur's stage festival at Liberio, and there she meets Mr. Leonhart whom she had not seen since her son returned from Paradis Island. Mr. Leonhart says he did not want to waste the honor he has been given, and asks about Mr. Hoover. Karina replies that Mr. Hoover had peacefully passed away and that he always spoke of how proud he was that his son Bertholdt devoted his all to Marley. Mr. Leonhart interrupts Karina when she mentions his daughter, assuring her that Annie is alive, since she had promised to come back.
Later on, she is seen in the crowd listening to the revelations about the true history of Marley. After Willy declares war on Paradis island, Eren Yeager's Attack Titan comes fourth, killing Willy and sending debris into the audience.