Rena is an extremely attractive young woman with chest-length dark colored hair (dark red in the anime) with bangs swept to the right side. As a high school student, she had shoulder length hair that hung on the right side. She has light colored or dark colored eyes (dark blue in the anime), a well endowed figure with large breasts, and full pink lips, traits that were passed down to her quintuplet daughters.

Because of her appearance, her beauty charmed every male and female student. Shimoda comments on Rena’s looks to Itsuki Nakano in different versions: in Chapter 57, she says, “that’s because Sensei was such… an incredibly beautiful woman.” In the English sub, she remarks that “Sensei was just that damn super beautiful,” while in the English dub, she notes, “Ms. Nakano was just that stunningly beautiful.” According to Jinnosuke Mudou in the movie and Chapter 109, he tells Itsuki, “you’re the spitting image of your mother when she was young.”

Rena is known to be a very serious, unsociable, strict, and stern woman, especially when it comes to teaching her students, as she would often punish them with iron-fist sanctions. Despite this, she was also very forgiving, and because of that, along with her striking appearance, she was adored by her students to the point that a fan club was created to worship her.

Rena was a single mother who raised five children. Before her remarriage to Maruo Nakano, she and the quintuplets lived in poverty similar to the Uesugi family. It is implied that the biological father of the quintuplets abandoned her and the children, which is why she advised her daughters to be careful when choosing men.

She worked as a high school teacher who was well-loved and respected by her students. Shimoda, one of her former students, was inspired by Rena and eventually became a lecturer at a cram school.

Rena passed away five years prior to the start of the story, on August 14, from an unknown terminal illness. Her death came as a shock to the quintuplets, whom she had continually reassured that she would be fine. After her passing, she was laid to rest at the Nakano family grave, where Itsuki Nakano visits most often.