The Cote d'Ivoire midfielder has become an integral part of City's side since arriving from Camp Nou for €30 million in July 2010, scoring 29 goals in 135 games for the club.
However in an interview with Sport, the 30-year-old revealed he had intended to see out his career with the Catalans and only a lack of first-team opportunities convinced him to leave.
"Barca were the club of my heart," the two-time African Player of the Year said.
"I had planned to retire there, to stay for many years. I've a lot of love for many people: [Andres] Iniesta, [Victor] Valdes, Xavi, [Sergio] Busquets... we were like a little family. [Gerard] Pique and [Carles] Puyol, too.
"I was 27 when I left, with enormous competition for places. I wanted to play more and not be on the bench. Leaving was the most difficult decision of my life, I loved that club and the fans. But now I am happy, at City I'm part of something very nice."
Toure has won the Premier League, FA Cup and Community Shield since moving to England and was amongst the scorers as City opened the season with a 4-0 win over Newcastle United last week.