Reginald Kastle, known as Ryoga Kamishiro in the Japanese version, was a human who died in a car accident, with the soul of the BarianNash continuing Reginald's life after his death.
Reginald and his twin sister Rio lived in a mansion with theirparents. One night, Reginald was chasing Rio around the house after she stole his Deck of Duel Monsters cards that his father gave him. Their fighting resulted in a suit of armor nearly falling on Rio, but Reginald pushed her out of the way, earning a scar on his right shoulder. One night, Reginald and his family were traveling in a car, which was hit by a truck driven by Chironex, who was fleeing from the police. All four were hospitalized.
All four members of the family died in the hospital. Just after their deaths, the souls of the BariansNash and Marin were transferred into Reginald and Rio, respectively. This was done by Abyss, after Nash and Marin were killed by Vector. This revived both siblings, but stripped Nash and Marin of their memories. Thus, Nash and Marin continued living as Reginald and Rio, with the doctors expressing shock that they were suddenly breathing again.
During Reginald's flashback, when Rio stole his Deck, several cards can be seen after she drops it.