Seiji Aino Edit
Akua's older brother, the two were very close as children growing. Akua was especially close to her brother that she wanted to spend more time with him many things, such as sports. This may have led to her becoming a tomboy who tends to react quite violently or negatively towards others who give her the wrong first impression. While Akua may never admit to it, she developed a "brother complex" for Seiji which also made become a bit of a tsundere whenever she is around her brother, being quick to act angry when someone, such as Guri, brings up her possible feelings for him. Because of this, she is also disappointed in Seiji's relationships with other girls, three of them no less, sparking a hint of jealousy, though she claims that him dating more then one girl bad and all of whom are incredibly bizarre in her eyes. Despite her claims and denial, Akua loves her brother very much and tries to look out for him as he has always done for her.
Akane Hiyama Edit
The two first encountered each other when Akane attacked Akua at the front door assuming she was another hussy trying to steal Seiji, but quickly changed her mood when Seiji tells her the she is his younger sister. Akane immediately becomes friendly by stating they are future sisters-in-law, but Akua was given the impression that Akane is a psychopath and leaves in a huff. Akua refused to accept Seiji being in a relationship with a crazy girl like Akane, and when they group went to the beach under Akane's request, she was left disappointed, constantly giving Akane the cold shoulder whenever she tries to bond with her.