A student at Yokohamabane High School. Both she and Theo hired Hamatora to find their missing teacher whose name was Yasuo Kitazawaby using all their savings. A while after that case they decided to work part-time at a hot spring where some of the Hamatora girls won a trip too, as well as another one of the locations of both Nice's and Murasaki cases.
She is very close to Theo, and is usually seen near to him. The two share a relationship akin to childhood friends or siblings.
Rei held Kitazawa in very high esteem, admiring him for his dedication, compassion, and what he did for Theo. She is shown to be very sad at his funeral, weeping over his casket. Her reaction to discovering Kitazawa's secret isn't as obvious as Theo's, but she feels betrayed after all he'd done for them in the past.