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 support them, seeing when she congratulated Reiner on becoming a Warrior and Gabi after hearing what she did during the Marley Mid-East War.
Like most Eldians living in Marley, she hates the Eldians from Paradis Island, believing them responsible for the Eldians' outcast status in Marley.
She also appears to be faithful when it comes to romance, as she had no other known lover after Reiner's father and wished to reunite with him years after their affair. However, the latter implied that it could be a personal revenge after he rejected her and their son because of their heritage.
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 cadet, so the pair would gain Marley citizenship and Reiner could reunite with his father. When Reiner announced her he had become a Warrior candidate, she warmly congratulated him, stating they were a step closer to Marleyan citizenship.
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.
A month later, 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 Bertolt 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.
- Reiner Braun - Karina deeply loves her son and has faith in him. His personal achievements, such as having become a Warrior, makes her proud. However, ever since his return from Paradis Island, she has been concerned about his drastic change in personality. Moreover, Karina does not show any concern about the shortened lifespan caused by the Armored Titan and even expects Gabi to inherit it.
- Gabi Braun - Karina is Gabi's aunt, seemingly caring for her as a part of her family. She has high expectations of Gabi, hoping that she will be able to inherit the Armored Titan from Reiner, and is proud that she is giving the Braun family greater recognition from Marley.
- Reiner's father - As the father of Karina's child and her previous lover, she likely cared a lot for him at one time. Even after being separated for many years, she seemed to have stayed faithful towards him, encouraging Reiner to become a Warrior in order to reunite their family. However, it is possible that Karina's true intention is to enact vengeance on him based on some previous action, as implied by Reiner's father himself.