Matsuri first met Yuzu when they were little. Yuzu was a lonely child, and noticed so was Matsuri, and thought they should be friends. Since then, they became like sisters. Matsuri was very clingy with Yuzu, wanting to take baths with her and invading her house to sleep with her, and when Yuzu would go out with other friends Matsuri would demand Yuzu to take her with her. Matsuri likes Yuzu a lot, and became very jealous when she realized how Yuzu felt for Mei, trying to win her back but it fails it is revealed that idea of losing her "older sister" Yuzu to Mei simply scared her which led her to acting so wrong. After that, Matsuri acknowledges that what she was doing was wrong and realizing how Yuzu and even Mei cared for her feelings decides to be her friend and supports Yuzu's relationship with Mei. Matsuri enjoys teasing Yuzu, which makes Yuzu embarrassed. Matsuri realizes Mei never wanted to take Yuzu from her, and starts seeing Mei as an older sister too. and since then they been on good terms. As such, Mei tutors Matsuri with her studies from time to time, and Matsuri helped Mei win a prize at the festival.
Harumi is distrustful of Matsuri, and warns Yuzu not to stay alone with her. Matsuri likes teasing Harumi, like she does with Yuzu and Mei. Matsuri notes that Harumi is very suspect, as she's always watching from far, which means she's afraid of getting hurt, and avoids conflicts. Matsuri says, however that she doesn't hate smart girls like Harumi.As time go's by Harumi starts to trust Matsuri to a degree they on friendly terms since they are usually seen hanging out Matsuri likes to tease Harumi, much to the latter's discomfort.It's possible she has a crush on Harumi.
She seems annoyed with her and her antics with her HaruYuzu fantasy.
Mayu is a friend of Matsuri, who talked to her after her boyfriend dumped her. Matsuri comforts her, but her actions afterwards imply that she was the one to cause that.
They have a very casual relationship, with Matsuri being a regular customer in his cafe since she was little.
She seem to be a little bit intimidated of her.