|Name (Kanji)||中山 真理子|
|School||Yamaboshi High School|
2-B (Post Michi Random)
|Homeroom Teacher||Gotou Ryuuzen|
|Seiyū||Akasaki, Chinatsu (赤﨑 千夏)|
|Novel Debut||Volume 4, Chapter 4|
|Anime Debut||Episode 1|
Nakayama, Mariko (中山 真理子) is a classmate and close friend of Iori. The two met during their first year at Yamaboshi High and have been inseparable ever since.
Mariko is an extroverted person; playful and peppy, not unlike her best friend. Mariko has proven to be a very loyal friend and was one of the few to stick up for Iori when Setouchi spread nasty rumors about her. However, Mariko did become temporarily disheartened when she witnessed Iori's negative attitude firsthand but quickly returned to Iori's side after she and Setouchi made up.
Mariko has green eyes and brown hair, which she ties into pigtails. She is very proud of her twin tails which are her trademark.
- Nagase Iori: Mariko's classmate and close friend. The two are shown to be quite playful with each other and Mariko was willing to defend Iori from Setouchi's rumors during the Michi Random arc.
- Ishikawa Daiki: Mariko's boyfriend. The two of them confessed to each other during the "love boom" after receiving some help from Taichi and Yui during Yume Random.
- Kurihara Yukina: A classmate and friend of Mariko's. In Step Time, Kurihara was upset that Mariko had failed to go on a date with Ishikawa since becoming a couple and sets up a triple date for her.
- Yaegashi Taichi: Mariko enjoys ganging up on Taichi along with the other girls during class and especially likes to tease him about Inaba.
- Mariko's hair is a lot lighter in the novel illustrations than in the anime.