Ayumi is Yuuki Hisamizu's underclassman who likes to tease and flirt with him, but can get easily flustered when the tables are turned on her. She shows her playful side exclusively to him whereas other boys in the school are given the cold shoulder when they approached her.

Spoiler

It is revealed during a flashback that she started having feelings for Yuuki since they became acquainted as study partners in junior high school.

Spoiler

Ayumi started dating with Yuuki after she accepted his confession on Christmas Eve.