A man is facing prison after being convicted of killing his sexual partner who he left tied up with a gas mask around his face.
Kevin Adams, 52, was found guilty in England of the manslaughter of his friend Dohoon Kim, 36, who was discovered dead on a bedroom floor with ropes around his hands, feet and neck.
The pair had taken mephedrone, known as M-Cat, and GHB, before engaging in "extreme" sexual activity at Adams' home in Exmouth Street, Swindon, Wiltshire, in June 2015.
Mr Kim died from a combination of the restriction of his airways and the effect of drugs both he and Adams had taken.
A jury at Bristol Crown Court found Adams guilty of gross negligence manslaughter following a 10-day trial. He will be sentenced on Monday.
Prosecutors said Adams had failed to ensure Mr Kim's safety during and after sex and then fell asleep without removing the gas mask or restraints.
Emergency services attended Adams' terraced home after he called 999, reporting that he had found Mr Kim unresponsive and not breathing.
Paramedics attended and found Mr Kim, from Slough, Berkshire, had been dead for some time and could not be resuscitated.
Pavlos Panayi QC, representing Adams, said his client had not chosen to fall asleep but had "passed out" due to drugs and physical exhaustion.
"Kim died two years and three days ago as a result of what everyone in this case will agree is a terrible, awful, tragic accident," he told the jury.
"Kevin and Kim met to have sex. They had met before and taken these drugs and had the same kind of fun in the past.
"No one was hurt before and no one wanted or expected that anyone would get hurt that night. They had met 12 times before. This was the awful, unlucky 13th time."
Mr Kim was born in South Korea and moved to the UK in 2001, meeting his partner Mark Ciccone a short time later. The couple began living together in 2012.
Jurors heard Mr Kim was a "submissive" who regularly met "dominant" men - including Adams - for sex, with the permission of Mr Ciccone.
He travelled from work in Slough to Adams' home by train and taxi on June 12, arriving there at about 8pm.
Text messages between the pair, who had met about two years previously on a dating website, refer to being "chemmed-up" - having sex while taking drugs.
A post-mortem examination found Mr Kim had low levels of GHB in his body and an "excessive" level of M-Cat.
Adam Feest QC, prosecuting, said Adams failed to remove the gas mask or restraints or check the condition of Mr Kim, who was left lying on the floor, before he went to sleep.
"Many things that could have been done, that could have been potentially life-saving, but not done in this case," he added.
Police analysed text messages between Adams and other sexual partners following Mr Kim's death.
"It is clear that he has a liking for extreme sexual activity, particularly bondage, corporal punishment and breath control," Mr Feest said.
"The practices which he indulged in are inherently risky, dangerous and unpredictable."
Adams had previously pleaded guilty to three counts of possession of Class A, B and C drugs.
Mr Panayi asked for sentencing to be adjourned until Monday to allow his client to "settle his affairs".
Judge Neil Ford QC agreed and granted Adams bail.
Speaking afterwards, Detective Chief Inspector Jeremy Carter, of Wiltshire Police, said: "This was a tragic and needless death of a man described by his work colleagues as an industrious and ambitious person who clearly had a bright future ahead of him.
"Kim had spent the evening at Adams' home address in Swindon where the pair had taken a cocktail of drugs before engaging in sexual activity involving restraint and bondage activity.
"Adams had a responsibility to look after Kim's welfare and he failed to do so with tragic consequences.
"The restraints which had been placed on Kim, together with the mixture of drugs both men had taken that evening, proved fatal.
"It was Adams' failure and his care towards Kim which ultimately led to his untimely death.
"Today the court has recognised this failure and he will now be sentenced having been found guilty of manslaughter with gross negligence.
"I would like to take this opportunity to express my sincere condolences to the family and friends of Kim."