Michael Edward Applegate, 43, flew from Seattle and arrived at Narita International Airport on Monday, according to the airport police.
But when he arrived in Narita – around 70 kilometers (43 miles) from Tokyo – He was planning to transfer to Okinawa where he was due to start a new job. – Airport authorities found it had a bullet in its checked luggage.
Applegate confirmed that the gun was his own, but he said he didn
The 43-year-old is in custody at the Narita International airport police station, although it has been violated by Japan's swords and firearms control law, which imposes an almost blanket ban on citizens owning firearms.
If he's charged and found guilty, he faces a minimum of three years and a maximum of 20 years in jail.
Under Japanese law, guns and bullets must be stored separately.
CNN has reached the United States Transportation Security Administration (TSA) for comment.
At the time, Japan's Transportation Ministry said it would fly into Narita International Airport with a firearm in it's carry-on luggage TSA. But it did not tell the TSA responsible and asked for the organization to take preventative measures.