Haruka has chocolate eyes with light brown hair that she wears tied up in a low bun.
Haruka is Chizuru's classmate, who is friends with Takane. Like her friend, she is not skilled at sports. The two wanted to befriend Chizuru but had a hard time talking to her due to Chizuru's cool and aloof personality. However, after playing volleyball with Chizuru, she and Takane became friends with her.
- Haruka's surname Koyama means "small" (小) (ko) and "mountain, hill" (山) (yama).
|Amusement Club||Akari Akaza • Kyōko Toshinō • Yui Funami • Chinatsu Yoshikawa|
|Student Council||Ayano Sugiura • Chitose Ikeda • Sakurako Ōmuro • Himawari Furutani • Rise Matsumoto|
|Teachers||Nana Nishigaki • Hatsumi Kitamiya • Shihoko Azuma • Tsubasa Minamino|
|Relatives||Akane Akaza • Tomoko Yoshikawa • Chizuru Ikeda • Mari Funami • Kaede Furutani • Nadeshiko Ōmuro • Hanako Ōmuro|
|Majokko Mirakurun||Mirakurun/Kurumi • Rivarun/Raika • Ganbō|
|Minor characters||Haruka Koyama • Takane Dezaki • Hiro Takaoka • Aoi Isurugi • Megumi Sonokawa • Ai Miwa • Miho Yaeno|