Kaya is of German ethicity, with light blode hair and blue eyes. She is slender. She has an adventurous and amicable demeanor with a traditionally feminine style of behaviour. She is friendly and approachable, traits that make her attractive to Ryuuji.
Kaya is a relative of Lilie, the player behind Cello. After the death of Lilie's parents, Kaya adopts her and acts as her legal guardian. In 2009, Kaya meets Ryuuji, the player behind Flugel, while he is in Germany. They eventually fall in love and marry. However, Kaya later dies, leaving Ryuuji to take care of Lilie.