Rei is a student at a fighting dojo run by a man named An, which may have been established to produce physically disciplined people for the creation of Guyborgs. She is first seen sparring with her brother Yuu. Their practice is interrupted when Gou Kazama walks into the dojo, asking about his brother. Gou gets into a fight with Dojo master An, causing Rei to rush to a computer to check the combatants achievements to see who is more likely to win. She and her brother aid Gou in his search for his brother Masato.