In the remote mountain village of Nagakushi, an elderly couple has raised two children — a boy and a girl — since infancy. The couple had always been childless until one night a prophetic dream led them to abandoned infants, and they took the pair in as their own. Eight years pass without anything unusual. Then the western capital suffers a catastrophe: an evil dragon appears and begins converting the city's people into oni, soul-devouring monsters that spread outward from the capital. They reach Nagakushi. The elderly couple's souls are taken. The two children, left unharmed, are now alone. Rather than flee, they make the decision that shapes everything that follows: they will pursue the dragon, recover the stolen souls, and bring the couple home. The first chapter of BS Shin Onigashima sends them into a world they have never left their village to see — already full of dangers neither is prepared for.