She has long hair.
She was best friends with Beniko Yukide in middle school, where they both attended the full contact karate club and were in love with Shin. On graduation day, she found Shin behind the school building about to meet Beniko who attempted to confess to him, and in her embarrassment accidentally knocked him out by shoving him into a tree. Later, her friend died in an accident, and she and Shin would date.
A month later, when Shin felt a heaviness in his chest and sought Rinne who revealed the numerous middle school buttons on his second button, she felt worried that Beniko was angry at her. But after revealing her past, Rinne allows the spirit of Beniko to meet and reveal her true motive to Mayu, which reassured her.