Mariko Nakamura is a friend of Suzume Mizuno as they both attend the same clubs together at Mochinoki Middle School. In the Japanese version, Suzume calls her "Mari-chan."

Mariko, however, is seen to be more conceded and obsessed with her appearance than Suzume tends to be, her importance, along with Kiyomaro's other friends' importance develops as the story progresses. She also has great cooking skills and is skilled in ping pong, even though Gash and Kiyomaro managed to beat her in ping pong.