football.london asked the former Golden Boot winner just how difficult that decision was after 10 years of wonderful memories in N17.
"It was the most difficult decision of my career. I have been here for 10 years. It’s a beautiful club with beautiful fans. I have such amazing memories," he said. "It was so hard to make the decision. I just felt like I needed a new environment to push myself to get more out of me I think I needed a little bit of change. 10 years is a long time.
"I came to north London as a kid. 23 years old, a very young age. A boy who couldn’t speak English. I leave this club as a grown man. Thank you to all the Spurs fans who have given me so much love. It felt like it was my home. It was one of the toughest decisions I ever made. I think it is the right time to leave. I hope that everyone understands that and respects that."
There were times on Saturday morning when he caught himself, teetering on the edge of breaking into tears, but managed to hold them in, never more so than when speaking about his friends within the club.
"I spoke with only a few guys, ones I've spent a long time with. Obviously they're disappointed, as a friendship or as a team-mate you'd be very disappointed if someone decided to leave, but in a respectful way," he said. "Obviously I'm very close with Ben so we've spoken about the future a lot of times.
"He fully respects my decision. So does everyone. What can I say? It's very, very hard to tell my team-mates because I sometimes probably spend more time with them than my family because we're travelling together, spending time together every single day at the training ground, five or six hours every day. I think we know each other so well.
"Everybody was disappointed but also in a way very happy for me. That was my feeling but I don't what they were actually feeling! They seemed happy but disappointed when I told them my decision."
As the press conference wore on, Son smiled more and more. He was the old Sonny, like a huge burden had been lifted from his shoulders. The relief of the release of the information was palpable.
Some of his team-mates and the coaching staff within Tottenham sensed months ago what was coming this summer. Son was utterly committed to ensuring his final season was a success, but those closest to him noticed the slightest difference, even if it was just a one percent change in how he viewed things.
Injuries hampered his final campaign and he was often playing through pain, but he continued to drive the team on even if his contribution was not as high as he would have wanted.
There is a misconception that Son is not a vocal captain and instead more of a leader by example like Ledley King was during his years at the club.
In fact Son is a talker and those within the dressing room say his greatest strength as a captain was unifying the squad. The ever-smiling South Korean would be seen with his arm around anyone, whether it was another leader like Cristian Romero or a youngster like Mikey Moore or an even fresher wide-eyed recruit sent from the academy into a first team session for the first time.
Son had time for everyone and he brought people together. Spurs have had some fractured squads over the years with cliques and arguments that ran deep, but it's no coincidence that during Son's time as captain the squad was the closest-knit it had been since the Mauricio Pochettino years.
In previous years the club could occasionally split into groups with the Spanish and French speakers off in their own spaces and the English players doing their own thing. Son though would bounce between the groups, a legend and a friend to all of them, and they naturally gelled together with him as their leader.
There's no way a team that suffered through the injury crisis that hit Tottenham last year and the dreadful league form that followed could have won the Europa League without being tightly-knit as a band of brothers rather than an assembly of individuals. Don't forget how young that Spurs squad was and Son played a huge part in focusing those young minds in those final months when it really mattered, even when he couldn't lead them on the pitch as a foot injury dogged him to the point where he had to retreat to the sidelines.
During one particularly difficult period for Spurs, as negativity threatened to seep into the camp as the media hammered the club for their sub-standard Premier League performances, Son called a meeting with the playing squad at Hotspur Way. During it he made it clear that they had to all stick together.
It was seen as a show of real leadership at an important time and many within the squad saw it as a defining moment last season in his captaincy as it galvanised a beaten, battered and injury-riddled side.
While there is disappointment at Son's exit among his friends at Spurs in terms of losing a grinning force of nature in the dressing room as well as a top player, there is a happiness for him to experience something new.
After a decade in one place, a change of scenery will be perfect for him. MLS has been ideal for Messi to remain in the spotlight and his best moments shared around the world with less focus on anything that declines as age catches up with greatness. The same will be the case for Son and he will be refreshed and reenergised for next summer's World Cup.
Sunday's game against Saudi Sportswashing Machine could well be Son's final match in a Spurs shirt. There is something beautifully poetic about that. He gets a huge send off in front of 66,000 of his country's fans inside the Seoul World Cup Stadium and it means his final competitive game in front of the Tottenham faithful was that night in Bilbao.
As he sank to his knees and wept on that pitch it all hit him in one go. The relief, the pride and the knowledge that he would leave Tottenham Hotspur in a better place than he found it. After 454 appearances, 173 goals and 101 assists, Son Heung-min had led them to a European title, the trophy drought was over. His job was done.