The 32-year-old man, whose name has not been revealed, was arrested last August after Tokyo police officers found him riding with two spot-billed ducks, known as karugamo in Japan, in his bicycle basket, the national broadcaster NHK reported on Saturday.
He told the police that he had caught and killed the ducks with bare hands at a park near Shinnaka River in Edogawa District. He said he planned to cook rice porridge with the ducks, because he was not enjoying Japanese food very much.
According to the investigators, the Vietnamese man, who came to Japan under a technical internship program in late 2017, claimed that he was not aware that the killing and eating of wild ducks is illegal and violated the wildlife protection laws in Japan.
Police have handed over the case files to prosecutors for further action, NKH reported.
The Vietnamese expat population in Japan increased four times from 2012-2016 and reached 232,562 last year, making it the fourth biggest minority group in the Northeast Asian country.
However, the reputation of Vietnamese people living in Japan has been tarnished following a Japanese police report last year that said they committed more crimes than any other foreign non-permanent residents in the country.