Daichi Yoshida, a military history buff as well as a comics artist of some repute back home, was eager to pick up a few vintage rifle parts while in Ukraine to take back to Japan.
He packed the items that he purchased at a military shop in Kyiv and informed security at Kyiv's Zhulyany Airport when he checked his luggage before flying out of the country on August 15, 2016.
Assured in Kyiv that all was in order, the 27-year-old Yoshida prepared for his long trip home, a circuitous route with scheduled transfers in Minsk and Abu Dhabi.
The journey, however, came to an abrupt, nightmarish end in the capital of Belarus, a country known for straying from democratic norms under authoritarian leader Alyaksandr Lukashenka.
Security personnel in Minsk searched his baggage and found the gun parts: 10 locks and four barrels from vintage bolt-action Russian-made Mosin-Nagant rifles dating back to the late 19th century.
But rather than mere antiques, Belarusian security saw something more sinister: arms parts suitable for contemporary weapons.
Suddenly, a confused Yoshida, who spoke not a word of Russian or much English, found himself facing charges of arms trafficking and smuggling.
He was given a 4 1/2-year sentence in a high-security prison, where his mother says he's struggling to "survive" after more than a year behind bars.
"He was completely destroyed psychologically. He didn’t understand where he was, and now he is suffering from depression," Yoko Yoshida tells RFE/RL's Belarus Service.
He's now being held in a prison in Vitsebsk, a northeast Belarusian city that is best known as the birthplace of the artist Marc Chagall.
In a letter scrawled on a scrap of paper, Yoshida tried his best in broken English to explain his plight:
"I've been in terrible condition for one year. My mental has got break. I remember everything which I saw."
The Japanese Embassy in Minsk would only tell RFE/RL that it was taking "all necessary and possible measures" to free Yoshida.
It's not the first case of its kind in Belarus.
A Frenchman was detained recently under similar circumstances, but with one big difference. Jolan Viaud was eventually released after a Belarusian court ruled that the single bullet casing found in his backpack did not amount to arms smuggling.
Viaud reportedly heard of Yoshida's fate while in prison. Aleksandr Lapshin, a Russian-Israeli blogger, said he actually met Yoshida during his own imprisonment in Belarus.
"The Japanese man was deeply upset. He is a well-known cartoonist in Japan. His name is Daichi Yoshida, and he wound up behind bars for nothing," wrote Lapshin, who was detained in Minsk in December 2016 and extradited to Azerbaijan in February 2017, when he was sentenced, but later pardoned, for illegally visiting Nagorno-Karabakh.
Armed only with his drawings, Yoshida had traveled to Odesa in June 2016 to take part in an art festival in the Ukrainian Black Sea port city.
Before departing from Kyiv in August, Yoshida visited the Parabellum military memorabilia shop.
"It is well-known in Ukraine. A shop. It is licensed to sell weapons, and if they sell parts, they are always deactivated," says Heorhiy Vchaykin, the head of the Ukrainian Freedom weapons-owners association. "Parabellum has been on the Ukrainian market for more than 10 years. It’s been checked hundreds of times by law enforcement agencies"
When shown a picture of Yoshida, staff at the shop said the face seemed familiar.
"We do sell historical weapons, and we have such parts for the Mosin rifle in stock," an employee said.
Before departing Kyiv's Zhulyany Airport, Yoshida asked airport security personnel whether it was OK to travel with the rifle parts, his lawyer explains.
Yoshida contends that airport security photographed each item and scanned his passport before telling him about 30 minutes later that all was fine.
But just hours later he was detained in the transit zone of Minsk airport after his bags were checked by Belarusian airport security and the incriminating arms parts were discovered.
Yoshida soon found himself spending months in pretrial detention at three prisons, including an isolation ward in Minsk, before going on trial in Minsk in April 2017.
Yoshida didn’t deny in court that the gun parts belonged to him. He readily admitted he had picked them up in the vintage military shop in Ukraine.
His lawyer, Dzmitry Shylau, says his client had no intention of violating the law and was only transiting Belarus. His mother says her son rarely understood what was going on around him.
"He did not know for months what was happening until we organized a translation for it," she says.
The Oktyabrsky District Court of Minsk nevertheless found him guilty of trafficking and smuggling firearms. The court sentenced him to 4 1/2 years in a high-security prison.
Yoshida says her son is suffering in Belarus's notorious prison system.
"He told me that the hygienic conditions in the prison are horrible. There’s no toilet -- just a hole in the floor in the corner of the cell," she said. "No toilet paper in the cell, and it's dirty and damp. The food is scarce, and what there is is not healthy."
Asked for comment by RFE/RL, the Japanese Embassy in Minsk wrote: "With regard to your questions, we would like to inform you that we are aware of the mentioned case. From the viewpoint of protecting Japanese nationals, we have undertaken all necessary and possible measures."
Shylau says the Belarusian court system is considering his appeal against the verdict.
"Help me," Yoshida writes in his letter from prison. "I filed a petition to the Supreme Court. But I do not believe in justice."