Rai is a supporting character in the Kurozuka anime. She is an adult woman with short blonde hair and blue eyes, and she belongs to the underground resistance movement known as Haniwa, which operates in the story's post-apocalyptic setting. She works alongside another resistance member, Karuta, in opposing the Red Emperors Army, the powerful organization that controls the ruined world. Her main contribution to the cause is intelligence work: she collects information about the enemy from various sources. She is not a skilled fighter, but she is courageous and willing to take risks in service of the resistance.

Early in the story, after the protagonist Kuro is wounded in a clash with the Red Emperors Army, Rai takes him to her apartment so he can recover. She then brings him to Izana, another resistance figure, who claims to be able to reunite Kuro with the woman he seeks, Kuromitsu. Following this, Rai continues to support Kuro and the resistance as they move toward the Red Emperors Army's headquarters.

Later in the narrative, Rai is captured along with Kuro by the Red Emperors Army. While they are held captive, it is revealed that the resistance member Kuon is actually a Red Emperors agent who had infiltrated Haniwa, and Kuon kills Rai. Her death occurs as the larger conspiracy involving Kuromitsu's plans, including her intentions regarding Kuro's body, is exposed. Rai's fate reflects the harsh costs of the resistance's struggle and the merciless nature of the forces arrayed against them.

In terms of abilities, Rai has little combat strength; her value lies in observation, information gathering, and personal bravery. Her role in the story is that of a loyal ally whose intelligence and support help advance the resistance's efforts, and whose death marks a significant turning point in the closing stages of the series.