The Japanese police have arrested a 73-year-old man in a rather extraordinary case. The man is suspected of keeping his son in a wooden cage for over 20 years. Yoshitane Yamasaki said he locked up his son, now 42, because he suffered from mental derangement and would sometimes become violent. The cage, 1m in height and less than 2m wide, was inside a hut next to Mr Yamasaki’s house in the city of Sanda. The son, who now has a bent back, is being taken care of by authorities. A visit by a city official to Mr Yamasaki’s home at the time alerted authorities to the 42-year-old man’s confinement. Investigators believe Mr Yamasaki began confining his mentally ill son from the age of 16, when he began to “act up”. For the time being, police have only arrested the pensioner for caging his son for 36 hours on 18 January. Mr Yamasaki has reportedly admitted all allegations, saying that he he fed his son every day and let him bathe every other day.