A pensioner has been arrested for allegedly keeping his disabled son locked in a tiny cage for more than 20 years.
The 73-year-old is said to have kept his son, now 42, in a wooden cage inside a hut next to his home in western Japan.
Yoshitane Yamasaki was arrested and handed over to prosecutors on Monday for further investigation, Hyogo prefectural police said.
Mr Yamasaki acknowledged to police that he had kept his son in the cage until January, when he turned himself in to city officials.
He was seeking advice on nursing care for his wife but revealed what he had done to his son, police said.
The officials visited his home and found the son sitting on a toilet sheet for pets inside the cage, which was slightly bigger than a coffin.
He was exposed from the waist down, though Mr Yamasaki told officials it was not usually the case and that he had bathed and fed his son every other day.
Mr Yamasaki told police he started confining his son when he became violent years ago.
Japanese media said the son was caged for more than 20 years, but police would not confirm that number.
Due to years of confinement in the 1m-high cage in which he could not stand up, the son's back was bent and he was nearly blind because of infections from the filthy conditions, according to the Yomiuri newspaper and other Japanese media reports.
Police said they were still investigating and declined to give details about the son's condition, except to say that he had no life-threatening injuries or illness and has since been cared for by a welfare centre.
Police are also looking into whether neighbours noticed his confinement and why it was unreported for so long if he had been violent and noisy.
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