Yuzu and Mei became stepsisters when Yuzu's mother married Mei's father, Shō Aihara. Yuzu is a month older than Mei. At first, Yuzu dislikes Mei, due to her aloof and manipulative attitude. But after Mei first kissed her, Yuzu resented her for a short time before coming to terms that she was somehow attracted to Mei. While the two of them have had very intimate moments with each other, for a time Yuzu thought it would be in Mei's best interests if she didn't pursue her romantically, feeling that Mei needed a sister more than she needed a lover. However, she grows to love her, eventually admitting that she wanted to be with Mei despite how cold and distant she could be. After both confessing their true feelings for each other she starts dating Mei.
She often gets frustrated with Mei's unpredictable sexual advances on her, yet makes it clear that she worries for her younger sister greatly. She does her best to be what she considers is a "good sister", but sometimes her actions derail due to her romantic attraction with Mei.
Yuzu is shown to being sensitive towards Mei's feelings; however, she struggles to communicate to Mei how much she means to Yuzu, and often this leads to many tense situations. Similarly, Mei struggles to understand Yuzu. Despite her desire to become closer with Mei, Yuzu remains completely oblivious to her own admirers.
Yuzu has a good relationship with her mother, supporting her in her new marriage to Shō despite how embarrassing she could be.
Shō is Mei's father, and Yuzu's stepfather. Yuzu is quick to accept Shō as her new father upon meeting him and develops a strong positive relationship with him. Seeing that his relationship with Mei has become strained due to his change in personality, Yuzu decides help them make up with each other.
Though at first they got off on the wrong foot after Yuzu saved his life he had gained a new found respect for her.
Yuzu and Harumi quickly befriended each other, due to their similar personalities and interests. Harumi always encourages and cheers Yuzu when she's down, and Yuzu enjoys talking and hanging out with Harumi.
Yuzu and Matsuri first met when they were younger. When Yuzu saw Matsuri moving in her neighborhood, she called out to her and that's where their close friendship began. Yuzu sees Matsuri as a little sister, and similarly, Matsuri sees Yuzu as her older sister. She cares for her deeply and tends to be concerned about her a lot. After a few years of not seeing each other due to Yuzu moving again, Matsuri got involved with dirty business online, which concerns Yuzu. They currently have a normal friendship with each other, but Matsuri likes to tease Yuzu, much to the latter's discomfort.
Himeko is Mei's childhood friend, who becomes jealous of Mei when Yuzu shows up and became Yuzu's rival over Mei's love, although they develop a more friendly friendship later on. Still, Himeko is annoyed by Yuzu's personality and disregard for the school's rules.
Yuzu first met Sara when both lost a train they had to get during a school trip. Fortunately, they were both going to the same place, so they took the train together, which Sara attributes to her "luck". They get along well, but Yuzu considers Sara "intense". Yuzu sees Sara's determination to go after her crush as an inspiration to go after her own crush, not knowing they both have a crush on Mei. When she finds out Sara is dating Mei, she decides she has to do something about it, even if it could end their friendship. Upon meeting Sara where she and Mei had gone, Sara asks Yuzu if she is willing to do what it takes to make things right between the two of them, going so far as to support Yuzu in her attempt to reconcile with her sister at the expense of her own happiness, claiming that she is not the one Mei's waiting for. They still maintain good friendship afterward Sara full heartedly supports Yuzu's relationship with Mei.
She first met Nina outside the hotel after returning her sister to her and was very thankful to her and they became friends Nina knew of Yuzu's feeling towards Mei's but still chose her sisters happiness over her friendship with Yuzu. She makes Yuzu promise she would support Sara's relationship with Mei, at this time Yuzu did not know that it was Mei who Sara is going out with. Nina was angry at Yuzu for trying to get in the way of Sara's and Mei's date and even goes as far as trying to stop her from interrupting their date. cause Nina knew if Sara finds out of Yuzu's feeling towards Mei's Sara will choose to support Yuzu's love for Mei over her own happiness. It gets resolved in the end and eventually maintaining a good relationship.
It's unknown exactly how Yuzu feels about Nene, but Nene looks up to her as a fan, going so far as to dye her hair like Yuzu's. Yuzu defends Nene from Mitsuko. Even after the ordeal they still remain friends hanging out from time to time and even invite her to a summer festival and for a summer trip.
They first met in summer supplementary classes and they became friends, they even hung out at a summer festival where she discovered Yuzu's and Mei's hidden relationship and decide to be supportive of Yuzu's and Mei's love by keeping it a secret and help it blossom.
Kana and Manami were friends with Yuzu during her middle school and before she moves schools, high school. Yuzu was a little bit jealous of them talking about there love life which why is she lies to them about having a boyfriend. She did reveal to them that she is dating, but she is unable to tell them she is dating a girl after they showed homophobic behavior in front of her, it's unknown how she feels about them now after this realization.
Yuzu was, at first, afraid of Mitsuko, but overcame her fear in order to defend Mei, Nene, and Harumi.
They have a good relationship. He supports Yuzu relationship with her lover, without knowing who that is.