| This article contains spoilers from the manga that has not been shown in the anime. Please continue reading at your own risks.|
Rena Nakano (
As a teacher, Rena was an incredibly beautiful woman that her beauty charmed every male students and female students. She has light-colored or dark-colored hair that is swept to the right and light-colored or dark-colored eyes.
Rena is known to be a very unsociable and serious person, especially when it comes to teaching her students, but she was also very forgiving and for that (as well as her appearance), she was adored by her students and there was a student fan club dedicated to worship her.
Itsuki was definitely close to Rena as Itsuki goes to her mother's grave on the 14th of every month. Rena also acted as a role model for Itsuki, who listens to her words, especially when it came to choosing men. Due to this, Itsuki aspires to become a teacher just as her mother once was.
Before remarrying Maruo Nakano, Rena was once married to this man. He is the quintuplets' biological father. It is uncertain what exactly caused them to split up, but it is hinted that he was a bad person. When she was alive, she advises the quintuplets to always be careful when choosing men. This shows Rena's regret for having married this man.
- Since Rena was a beautiful woman, it is the reason that the Nakano quintuplets have beautiful appearances as they all have inherited Rena's beauty.
- Rena was originally a single mother. Before the remarriage to Rena's current husband, she has been living in poverty like the Uesugi Family.
- Rena passed away five years prior to the beginning of the series on August 14  and it is unknown how Rena died or what the cause of her death was.
- But, it is hinted that she died from an illness due to overworking and taking care of the quintuplets as a single mother. [no citation]