An "always happy" teenager may have died when an experiment with a ligature went wrong, an inquest has heard.
Nathan Smith was found hanging from his bed by his step-father
Nathan Smith, 13, from Aberdulais, was found in his bedroom with a tie around his neck, hours after being made man-of-the-match by his football team.
He died in hospital a few days later in January and police concluded no-one else had been involved.
Recording a verdict of accidental death, the Neath coroner said the truth of the tragedy may never be known.
On the day of the accident, the teenager had returned home excited after playing for his local team Cadoxton AFC and winning the man-of-the-match award, the inquest was told.
Stepfather Mark Smith said Nathan had then gone straight out to nearby fields to play football again with friends.
"During the day he was himself, smiling," said Mr Smith.
He said his stepson, a pupil at Llangatwg Comprehensive School, was told to return home for his tea at 4pm but had come home early and went upstairs for a shower.
But when Nathan failed to come to eat after his shower, Mr Smith had gone to his bedroom and found him hanging from his bunk bed.
"He looked like he was standing. I untied the tie from the bed," Mr Smith said.
He told the court he shouted down to Nathan's brother to get a local first-aider and an ambulance was also called.
Nathan was still alive when taken to Morriston Hospital, Swansea, but died of asphyxiation within the week.
"There was nothing on that day out of the ordinary," said Mr Smith. "He was always happy, you can ask anyone."
Coroner Dr David Osbourne said there was no evidence which indicated Nathan had taken his own life because everything on the day of the accident had gone "extremely well".
"There is no part of the evidence which indicates in any way that Nathan was anything other than a happy, outgoing young 13-year-old boy," he said.
"What he was doing we cannot say but it is not unknown for young boys to experiment with ligatures and that sort of thing.
"We can only assume on this occasion Nathan was playing around with this ligature around his neck and something went wrong."
At the time of his death, his family issued a statement which said Nathan was a "happy boy and was always smiling".
"He loved sports, especially football and he supported Arsenal and the Swans. He wanted to teach sport to children less fortunate than him."