Matsuri is a middle school student who has known Yuzu since childhood. She makes her first appearance in chapter 6 and is described as being pretty with headphones around her neck. She behaves slyly and falsely towards an unidentified friend, inviting Yuzu and Harumin to karaoke at an arcade. Although Harumin seems wary and suspicious of her, Matsuri eventually kisses Yuzu in front of Mei, revealing her romantic interest in the latter. In addition to this, Matsuri earns money by selling masturbation videos she finds online through a phone app, claiming they are hers. She views men as dense and easily manipulatable.
Annoyed with her "date" being interrupted by Mei, Matsuri meets up with Mei later and tricks her into kissing her (though she expected Mei to hit her) and has two delinquents take a picture of the kiss, which is implied to be used as blackmail in the future.
As of Chapter 10, when on a "date" with Yuzu in a shopping centre, she tells Yuzu in front of a crowd that she loves her, and it is heavily implied that it is romantic in nature, but her feelings were not answered due to Yuzu being in love with Mei.