Himeko and Mei are childhood friends. She is very possessive of her and becomes jealous when Yuzu appears in her life. They have been friends since elementry school and were very close until one day when Mei grew depressed after her father left, they still remaind friends.
Yuzu is Mei's stepsister, who Himeko dislikes due to her unruly nature and her closeness to Mei. They become rivals for Mei's affections. Over time, though, Himeko becomes less antagonistic towards Yuzu, although she is still annoyed by Yuzu's disregard of the school's rules. She does worry and cares about Yuzu's well being in such as when Mitsuko decides to force Yuzu into an election race against Mei for the Student Council presidency.
Like with Yuzu, Himeko dislikes Harumi for her attitude. Harumi, however, seems to like Himeko, and enjoys teasing her.
Glasses-Senpai: They are both Vice presidents to Mei's reign. They seem on good terms with one another.