Aika was first introduced when Ryoko was taking her driving test, telling Ryōko she doesn’t deserve to have a driver's license. She gets off to a rocky start with Ryoko and Sawako when they first meet, but gradually she becomes friends with them. Being a veteran street racer, she is a very skilled and versatile driver not only in her own car, but in many different types of vehicles (such as driving a large truck, Ryoko's AW11, a Honda CRX, and riding a motorcycle). She seems to be a very solitary person and is portrayed as a tomboy. Aika works as a truck driver as her daily job. She was mistaken to be the "Speed of Sound Beautiful Girl" because of her exceptional driving skills.