An autistic British teenager has been detained on drug smuggling charges in Japan, his sister has claimed.
Sean Stephenson, 18, disappeared unexpectedly on Father’s Day for a ‘sightseeing trip’ to Canada.
But, after an onward flight to Japan, he was arrested on June 21 with a locked suitcase alleged to contain more than a kilo of methamphetamine.
His sister claims that he ‘acted under pressure’ from British gang members who exploited his autism and threatened to break his legs.
Sean, from Charlton in South East London, was diagnosed with autism spectrum disorder (ASD) aged five, and had to be put on a reduced timetable due to his struggles at school.
His family insist he has never broken the law, is not involved in gangs, and must have been coerced and threatened into allegedly transporting drugs due to his much lower mental age.
Desperate for any evidence to clear his name, even if inadmissible under Japanese law, Sean’s family have gone to the Metropolitan Police and the National Crime Agency (NCA) to report their concerns.
But the family have been sent from pillar to post by the two organisations, they claim, both of whom have tried to pass the buck to the other.

Sean Stephenson (pictured), 18, disappeared unexpectedly on Father’s Day for a ‘sightseeing trip’ to Canada , but after an onward flight to Japan, he got arrested on June 21 with a locked suitcase containing more than a kilo of methamphetamine, it is alleged
‘I have not eaten. I have not slept. I’m a nervous wreck,’ Sean’s 33-year-old sister Ami Lee said, with just over a week before Sean goes in front of a Tokyo judge.
‘I am worried because my brother has [bad] mental health. I am scared we are gonna get a call to say “Your brother has taken his own life”.
‘That is my biggest fear when he’s innocent. If he was not innocent I would still be trying to help, but my brother is innocent. I just want to get him home. If I can’t get him home, the least I can do is try to get help.’
Ms Lee claims her brother has told her he was recruited by a gang in London and ‘forced’ to transport drugs across borders.
Since his detention, Ms Lee said Sean, through his lawyer, said that he was followed to Heathrow Airport and received threats to ‘break his legs and hurt his family’ if he did not get on the first flight to Canada.
Ms Lee also said Sean has claimed he was threatened with a broken bottle of Smirnoff Ice around two weeks before his arrest. Sean told her police were called out to the incident on June 10th, but he did not press forward with a criminal complaint.
‘He’s not in a gang, he’s very very vulnerable,’ Ms Lee said, ‘He’s quite a people pleaser. He would do anything to please people and make friends because Sean has got no friends. He’s very about his family.
He’s got nine nieces and nephews. He’s more on their level. My sister is 18-years-old and she does not come around and play tag or it with people.’

His sister claims that he ‘acted under pressure; from British gang members who exploited his autism and threatened to break his legs
Ms Lee also said Sean has a history of self-harm, suicide attempts, and other medical conditions.
Sean’s family have no idea who got him involved in alleged drug smuggling.
Experts on county lines have long warned autism is a risk factor in gang grooming, with autistic young people seen as easy prey due to their desire for friendship, and difficulty detecting lies and manipulation.
The FCDO has confirmed it is supporting Sean and is in contact with Japanese authorities.
Last year Australian national Donna Nelson was jailed for six years after she was found guilty of smuggling 2kg of methamphetamine into Tokyo in 2023, despite her claims she had been the victim of an online romance scam.
Prosecutors had asked for a 10-year sentence and $30,000 fine after she was caught with the drug concealed in the bottom of her suitcase.
The case highlighted what some commentators have called the ‘hostage justice’ system, due to Japan’s 23-day pre-charge detention period.
A 2023 Human Rights Watch article about Japanese justice focussed on reports of coerced confessions, the refusal of bail, police questioning without the presence of a lawyer, and the denial of family visits.
Sean’s mum Star Lee, 57, added: ‘I’m just so sad for Sean. I can’t explain how I am feeling. It’s a traumatic experience for all the family. We have not been allowed any direct contact with him.
‘We hear all these bad things about prisons abroad. We don’t know what’s happening and we are just praying he is safe.’