Rei is a girl with a heart and appearance as cold as ice. Of the girls in class 1-C, Rei is the most mature one. Threatening bodily harm is Rei's way of enforcing order in the classroom with Himeko being her usual target. She's the one to put Becky in her place when she gets out of hand and also the one to lure Becky out from behind the curtain with candy after she's put the fear of God into her. Rei has the second highest GPA in the entire school and works four days per week at a Chinese restaurant. Despite her apparent coldness, Rei is often the one to teach Becky important moral lessons.
She has also shown herself to have a greedy streak as when during the school festival she purposely made it so their classroom was the most popular so that she could reap the profits later, something she was unable to do since all profits went to charity.