Social media star and Britain's Got Talent judge KSI has announced he is leaving the YouTube collective Sidemen after 13 years.
KSI, whose real name is Olajide Olatunji, has made football, comedy and challenge videos with the group - which has 23 million YouTube subscribers - since 2013.
His spokesperson confirmed to the BBC that he was leaving, after many of his followers voiced suspicions that it was a stunt. Sidemen said it "came as a surprise" but wished him well.
"This is honestly the hardest video I've ever had to make in my life," KSI announced on YouTube.
"I've gone back and forth on this decision for a very long time," he added. "I've spent months trying to figure out what the right thing to do is.
"But after a lot of thought, I've decided that I will no longer be doing Sidemen videos. Today, 31 May, will be my final Sidemen video."
KSI, who appeared in Saturday's final of ITV's Britain's Got Talent, said he remembered the group's early days, and that he had "no idea that tens of millions of people were going to be watching us on the channel".
"We built something that none of us ever thought was possible especially back then when we were making random videos together and playing GTA," he said, referring to Grand Theft Auto.
He added that "nothing bad has happened" between him and the group.
"This decision is completely my own," he said.
"Over the last few years, I've felt myself being pulled in a lot of directions than ever before. Between everything else in my life, I feel like I've been running at full speed, at 100mph."
He went on to thank each of the group's other members Simon Minter, Josh Bradley, Vikram Barn, Tobi Brown, Ethan Payne and Harry Lewis, saying they "deserve somebody who can give 100%".
In a statement posted on social media by Sidemen, the group said they were "sad to share the news" that KSI had "decided not to continue".
"We had an amazing time on this journey with him and we wish him all the best with his future endeavours," they said.
"This came as a surprise to us and we know it will be an adjustment for you, but we've got lots of exciting stuff planned that we can't wait to share."
The collective have more than 140 million YouTube subscribers between them, with KSI the most widely recognised.
Their most popular video is a challenge where they divided into two groups and took holidays on budgets of $20,000 (£14,867) and $200 in Europe. It has had more than 100 million views.
Other popular videos include a "Sidemen Tinder" dating series, eating challenges and comedy roasts.
They have hosted charity football matches that have raised millions of pounds for charity and launched their own fried chicken chain, clothing, alcohol and cereal.
Some fans initially dismissed KSI's claim that he was leaving the group, believing it to be a stunt, but later many started posting tributes under his YouTube video.
"Thought it was fake at first, but looks like it's real. Still don't want to accept it though," one wrote.
"Good luck on the rest of your journey JJ! Takes courage to make this next step. Don't forget where you came from and how hard working you are as well," another said.
KSI started making videos in 2008 and rose to fame as an online streamer. He has more than 18m subscribers to his personal YouTube channel.
He is also a musician, former boxer and recently bought a minority stake in Dagenham & Redbridge Football Club.
