The real Ryo Asuka was the son of Professor Asuka and an unnamed American woman. He died an unspecified amount of time before the start of the manga, and his identity is then assumed by Satan.
Appearance
Ryo Asuka was a half-Caucasian half-Japanese young man with short, well-kept blonde hair and blue eyes. He was an attractive young man with chiselled features as well as a broadened nose. Ryo was tall and healthy for his age, standing nearly the same height as his father. His style of dress was of formal casual including a collared shirt and khakis.
History
He was born sometime in the 1960's. Apparently, his mother died at some point in his childhood. When he was 17 years old, he lost his own life in a car crash. Ryo is later referred to as the demons' first victim, so this "accident" may well have been planned in advance by the demon forces.
After his death, the demoness Psycho Jenny wipes Satan's memories and replaces them with those of Ryo, modifying them slightly to suit their goal to infiltrate human society. "Ryo" never suspects his true identity until he comes across a photo album showing a Ryo Asuka who he does not recognise as himself. He then reads about the real Ryo's death; during his ensuing identity crisis, a horde of demons led by Psycho Jenny invade the Asuka home and restore his true memories.