Kazuki is Azum'as classmate and demonstrates that he is his best friend, and possibly only close friend. They met before the opening ceremony of the school in their first year. Kazuki assuming Azuma was older than him, asked him for instructions until it was later discovered that Azuma was the representative of the new students, and it seems that they have been friends since then.
Kahoko is the main protagonist of the series, and Yunoki was one of possible love interests in the dating simulation game. In the manga and anime, Kahoko's personality and her vision of the world slowly attracts Azuma to her, to the point that she is the only one that he has revealed his dark side also. While that he pretends to be his flirtatious bullying and harassment towards her as "jokes" and jokes, that evidently shows jealousy and contempt when he learns that she asked Tsukimori and Annibali to go to an "appointment" to the amusement park with her (referred in chapter 35 of the manga). While Aoi Kaji was kissing the hand of Hino, Yunoki showed jealousy as he watched him. He usually refers to her as ' Hino-san ' in front of others and simply Hino in private (He calls her Kahoko later in the anime).
Miyabi is his younger sister, and the only one of Azuma's siblings introduced so far. Evidence shows that they care about each others well-being.
One of Azuma's candidates of marriage , she was fascinated by him as a child and decided to become his wife. Azuma, however is not really interested in that idea and enlist the help Kahoko to dissuade her by passing Kahoko off as his lover. Ayano studies in the same school as Miyabi, though it seems that Miyabi herself isn't too fond of Ayano.