She has short hair, and remained wearing her middle school uniform as a ghost.
Back in middle school, she and Mayu both attended the full contact karate club and were in love with Shin Munakata. On graduation day, she asked Shin to meet her behind the school building so she would confess to him, but Mayu found him before, so she hid herself for she knew that they were in love with each other. But after Mayu got embarrassed and accidentally knocked him out by shoving him into a tree, she took the chance to take the second button of his uniform while he was unconscious and keep it as a memento (for girls can receive these as trophies if they confess to boys at graduation ceremonies). But then she felt bad about it, and died in an accident as she was worried. However, her spirit lingered, hoping to return it.
She would try to put it back onto Shin when he and Mayu started dating, but continuously repeated that action, causing Shin to feel a heaviness in his chest. When Shin and Mayu sought Rinne and recall their past, Rinne allowed Beniko to speak to Mayu and return the second button one last time, which allowed her to pass on.