TOKYO (AFP) - A decade-long legal battle in Japan has ended in victory for parents sued by relatives of an elderly biker who died over a year after dodging a football kicked into the road by their son.

The country's top court said Thursday the couple were not liable for the freak accident, overturning a high court ruling in which they were ordered to pay 11.8 million yen (S$133,048) to the pensioner's family.

The decision came 10 years after the biker, a man in his 80s, crashed when swerving to avoid a football the then-11-year-old boy had been playing with at a primary school in Ehime, western Japan.

The biker died 18-months later from pneumonia his family said was directly linked to injuries he received in the crash. They filed suit, demanding 50 million yen in compensation.

"It was 10 years of agony for us," said a written statement issued by the father of the boy, who was not named publically. "We are relieved."

There have been numerous other cases in which Japanese courts have found parents financially liable for injuries resulting from the actions of their children.

In 2013, the high court ordered the mother of an 11-year-old boy to pay 95 million yen compensation after the child collided with a woman while riding his bike.