Police in Gunma Prefecture are looking for the owner of ¥42.51 million in cash that was found in garbage at a dumpsite in the city of Numata.
The cash was found at around 2:20 p.m. on Tuesday at the site, which is operated by a local waste transport firm, the Gunma Prefectural Police said.
One of the firm's employees found the cash while sorting trash. The 63-year-old male worker reported the discovery to his manager, and later to the police.
According to investigators, the chunk of garbage that contained the cash was believed to have been collected elsewhere as the waste firm only handles sorting operations.
The police also said the cash may have been thrown away accidentally, and they are treating the matter as a case of lost and found.
The latest incident adds to the world's perception of Japan as a country with a relatively low crime rate and honest people.
Under the law, anyone who finds money and reports it to police is entitled to a reward of 5 to 20 percent of the amount if the owner claims it.
If no one claims it within three months, the finder can theoretically claim the entire amount.