At first, Ruu was very quiet and cautious of people since she had suffered horrible trauma inside her school, as she was the only survivor. But after she recovered, she was still generally quiet and possibly mute or just shy, and it is also likely that she have stopped speaking much due to the trauma she suffered.

It also seen that, due to her trauma, she sometimes begins to panic and scream, but Yuuri Wakasa comforts her when this happens.[2][3] Most of the time to always, she'll stay by Yuuri