Mr Kato's relatives told police that he had "confined himself in his room more than 30 years ago and became a living Buddha," according to a report by Jiji Press.
But the family had received 9.5 million yen ($109,000: £70,000) in widower's pension payments via Mr Kato's bank account since his wife died six years ago, and some of the money had recently been withdrawn.
The pension fund had long been unable to contact Mr Kato.
HT MR