There are very few public trashcans in Japan. When I'm out and about in in Japan, I keep a plastic bag in my daypack to store trash. I was so excited to find a trash can in Tokyo that I took a photo of it. It's on Omotesandō in front of the Kiddy Land toy store:
Anyway, Sora News 24 reports that a police in Kamakura (about a 40-minute train ride from Tokyo) saw Anthony Tanaka (37), a U.K. citizen, toss his used takeout food container into one Japan's distinctive red post boxes. The boxes say POST in English, which you would think a person from England would be able to read, but the alleged litterbug claims he thought the mailbox was a trash can.
The police believe Tanaka may have been the person behind the other recent mailbox dumping incidents in Kamakura. Violation of the Waste Management Law carries a potential penalty of up to five years in prison and a fine of up to 500,000 yen (US$4,830), though the broad nature of the ordinance likely means that jail time is reserved for commercial/industrial-scale offenses or those involving harmful materials, which wouldn't apply to Tanaka. He may also face additional penalties for violation of Japan's postal laws, since the incident for which he was arrested involved a mailbox.