"I think it was one of the most difficult decisions I've ever made in my football career. Playing football and being with one team for 10 years is something I am very proud of, but I think I gave my all to the team every single day.
"I did my best on the field and off the field, and by winning the Europa League, I thought I'd done everything I could and achieved. That was probably the biggest reason (why I decided to leave the team)."
Son has made 454 appearances for Spurs and scored 173 goals. He won the Premier League Golden Boot in the 2021-22 season.
"I was so grateful that the team helped me a lot with this decision and respected my choice," he added.
"It was my favourite place for 10 years, and it was the place where I grew a lot as a football player and a person, so I have a very grateful heart."